Hi anabelian,
Welcome to the Mattress Forum! 
Yes, your post location is just fine. :cheer:
I think that you may have already found this, but you can read more about Amerisleep and their sister companies and their so called “expert sites” that pose as being independent review sites in post #2 here and the posts it links to. A forum search on Amerisleep (you can just click the link) will bring up will bring up all the forum posts that mention them as well.
I’ll address some of your questions directly, but much of what you’re asking has to do with “what” to select, and I focus more on the “how” to select. Let me post some general information first on guidance for selecting a mattress.
The first place to start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones.
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well he will sleep), durability (how long he will sleep well), and the overall value of a mattress compared to your other finalists based on all the parts of your personal value equation that are most important to you (including the price of course and the options you have available after a purchase if your choice doesn’t turn out as well as you hoped for).
Outside of PPP (which is the most important part of “value”), the next most important part of the value of a mattress purchase is durability which is all about how long you will sleep well on a mattress. This is the part of your research that you can’t see or “feel” and assessing the durability and useful life of a mattress depends on knowing the specifics of its construction and the type and quality of the materials inside it regardless of the name of the manufacturer on the label or how a mattress feels in a showroom or when it is relatively new so I would always make sure that you find out the information listed here so you can compare the quality of the materials and components to the durability guidelines here to make sure there are no lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress before making any purchase.
As it seems that you may be in a bit of a time crunch with your impending move, you may wish to focus on the simplified manner of choosing the “best possible” mattress. This comes down to FIRST finding a few knowledgeable and transparent retailers and/or manufacturers (either locally or online) that sell the types of mattresses that you are most interested in that are in a budget range you are comfortable with and that you have confirmed will provide you with the all the information you need about the materials and components inside the mattresses they sell so you will be able to make informed choices and meaningful comparisons between mattresses and then …
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Careful testing (hopefully using the testing guidelines in the tutorial) to make sure that a mattress is a good match for you in terms of “comfort”, firmness, and PPP … and/or that you are comfortable with the options you have available to return, exchange, or “fine tune” the mattress and any costs involved if you can’t test a mattress in person or aren’t confident that your mattress is a suitable choice.
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Checking to make sure that there are no lower quality materials or weak links in a mattress you are considering relative to your weight range that could compromise the durability and useful life of the mattress.
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Comparing your finalists for “value” based on #1 and #2 and all the other parts of your personal value equation that are most important to you.
A higher BMI presents special challenges and generally requires firmer materials (in the support layers especially). This could be firmer latex or innersprings (the type of support component would be a personal preference and in the right design either could be suitable) or even a zoned construction. The same overall guidelines apply with higher weights though that PPP (Posture and alignment, Pressure relief, and Personal preferences) along with using high quality durable materials that will maintain their feel and performance for longer periods of time are the way to make the best choices. Heavier people in general will need firmer and thicker comfort layers and firmer support layers than those who are lighter and because no materials will last as long with much higher weights the quality and durability of the materials and components is even more important than normal. I wouldn’t “rule out” any types of mattress and base your choices on your own personal testing. Post #3 here has more information and suggestions about heavier weights that is worth reading.
Higher BMI ranges will need more durable materials and components in a mattress and in a BMI range of 30 or higher I would include any 1.8 lb polyfoam or 4 lb memory foam as a “lower quality/density” material (relative to a higher BMI only) and minimize their use to a total of “about an inch or so or less” in the mattress.
Polyurethane foam: If your mattress is one sided then I would look for 2.0 lb per cubic foot density or higher. If the mattress is two sided then I would use a minimum density of 1.8 lbs per cubic foot or higher.
Memory foam (or gel memory foam): If your mattress is one sided then I would make sure that any memory foam is at least 5 lb per cubic foot. If the mattress is two sided then I would use a minimum density of 4 lbs per cubic foot.
Shoulder and arm issues can come from many sources, such as a mattress that is too firm and puts direct pressure on the shoulders, the shoulder blades, or on the back muscles and can also cause soreness or numbness and tingling in the arms. It can often come from postural issues, or is sometimes unfortunately can be an issue associated with a higher BMI. Shoulder issues can also come from sleeping in the same position for a longer period of time than normal. If the mattress is too firm, then if you sleep on your side your shoulders may not sink in enough to relieve pressure and your upper body can “twist” away from the pressure so your upper body is “twisted” more forward while the lower body is still on its side. This spinal twisting or torsion can twist the spine in the upper body and lead to soreness in the area of the twist. There is some much more detailed information, including some sleeping postural tips, on shoulder and arm issues in posts #2 and #3 here .
I would also make sure that your pillow is the proper thickness to keep your neck in a more neutral alignment. Using a body pillow can be a good thing and resting your free arm upon that can be helpful. Placing a pillow behind you to slightly lean against can also take a bit of stress off of your shoulder joint area.
Most “hotel mattresses” tend to be firmer overall, with softer “top of bed” products. Having firmer deep support would make sense for someone with a higher BMI. Regarding pillowtops, they are a construction process and not a comfort designation. If you had a mattress sag and it was tailored as a pillowtop, this sagging was most likely due to the lower density foams used within the pillowtop panel, although some manufactures do a poor job of constructing their pillowtops as well.
I wouldn’t focus much on the brand name, as you want to focus more upon the componentry inside of the product. Unfortunately, the major brands such as Sealy/Stearns & Foster, Simmons, and Serta all tend to use lower quality and less durable materials in their mattresses than most of their smaller competitors that will tend to soften or break down prematurely relative to the price you pay which is why I would generally suggest avoiding all of them completely (along with the major retailers that focus on them as well) regardless of how they may feel in a showroom along with any mattress where you aren’t able to find out the type and quality/durability of the materials inside it (see the guidelines here along with post #3 here and post #12 here and post #404 here).
Latex will be the most resilient (best “bounce-back”) of the foams, followed by true high-resiliency polyfoam, and then high density polyfoam. If you end up selecting a product using memory foam, you’d want to specify something that was faster-responding and also something that was less temperature sensitive impacting the viscous nature of the foam.
Memory foam would be the best foam at deadening motion. Latex also is good at this, but not as good as memory foam. A combination of either with a pocketed coil spring unit can also do quite a good job at deadening motion (see post #18 here). All the layers and components in a mattress will have some effect on the feel and performance of all the other layers and the mattress “as a whole” so the best way to test for motion isolation is your own careful testing on a mattress using the testing guidelines in the tutorial post (with both of you on the mattress) because a mattress that may be “motion isolating enough” for one couple may not be as suitable for another couple that is more sensitive. The bed frame/platform base you use will also impact motion transfer. The more solid the base unit, the less motion transfer that will be felt.
Polyfoam, memory foam and latex will all off gas something, and being organic certified doesn’t speak to that. Most people concerned with “organic” materials are usually concerned more with “safety” than whether the materials have an actual organic certification and they usually aren’t aware that an organic certification isn’t the same thing as a safety certification. There is more information about the three different levels of organic certifications in post #2 here and some of the benefits of an organic certification in post #3 here and there is more about the different types of organic and safety certifications such as Oeko-tex, Eco-Institut, Greenguard Gold, C2C, and CertiPUR-US in post #2 here and more about some of the differences between organic and safety certifications in post #2 here and there are also some comments in post #42 here that can help you decide whether an organic certification is important to you for environmental, social, or personal reasons or whether a “safety” certification is enough.
If you are going to shop locally, you can do a forum search for the city you’re moving to in New Jersey (or the closest major city) and see if there is a listing on the site of some retailers you may wish to visit. Also, among the site members closest to you that you may wish to visit would be Dixie Foam Beds and Scott Jordan Furniture in NYC, and the Shovlin Mattress Factory in Fanwood, NJ and Urban Natural Home Furnishings in Paramus, NJ.
If you are considering looking online, a good place for you to start could be to use the experience and expertise of the members listed in post #21 here who are all very experienced and knowledgeable and specialize in providing the type of help and guidance on the phone that can help you make good choices for a higher BMI. There are a wide range of latex and memory foam options included in the choices and I think highly of the advice that these companies provide.
Hopefully this helps point you in a proper direction.
Phoenix