Hi JZJ,
Welcome to the Mattress Forum! 
I can help with information about “how” to choose a mattress, but not “what” to choose. It’s not possible to make specific suggestions or recommendations for either a mattress or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort”, firmness, or PPP or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience.
Regarding limiting links, you’re asking quite a few questions here, and it isn’t possible to address all your concerns without linking to various sources, and this thread will be visited by others doing their own research, but I’ll attempt to make my replies to you in a more concise manner and then if you should desire to “flush out” those responses you can always investigate further by clicking upon any hyperlinked material.
This mattress is all polyfoam except for 2" of Talalay latex on top. There is no meaningful information about the density of the foams used in the mattress on their web site, and you would need to find out that information before being able to make an educated decision about that mattress. The information you need to learn about is listed here. I’m not sure if you’re interested in learning about “What’s Safe Enough For Me”, as it is a bit of a complex subject, but if you are there’s more information here. Latex will be the foam that tends to pass the more “strict” safety certifications, so you may want to stick with that as you mentioned earlier.
While Consumer Reports may be a good source of information about more “objective” purchases, I would consider them to be an unreliable source of information or guidance about purchasing a mattress and their “ratings” are somewhat nonsensical and meaningless. My thoughts are also shared by most of the more knowledgeable people in the industry (see post #5 here for an example). You can read more if you like in post #2 here and in this topic. Review sites that amalgamate mattress reviews from all around the internet, such as Sleep Like The Dead, and then “rate” mattresses (and other products) based on these amalgamated reviews, don’t take into account the quality of materials within a mattress and also are not a reliable manner in which to select a mattress. That’s one of the reasons that this site isn’t a mattress review site, and instead focuses upon teaching how to select a mattress.
Yes, it is possible.
Agreed, marketing doesn’t tell you anything about quality or durability.
Many online vendors will have generous exchange/return policies, and you’ll want to confirm those policies before considering any purchase.
Because of your physical issues, a detailed phone conversation with any company you are considering will be your best starting point. Their detailed knowledge of their mattresses and how they fit with different body types and sleeping positions along with your feedback from local testing, a customer base of many people that they can use as reference points, and any exchange, return, or any options they have available to customize a mattress after a purchase can help lower the risk of an online purchase. They can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs, options, and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
Per your earlier supposition, latex could be a good choice for you with its ability to provide pressure point relief, offer good surface support and have the ability to pass more “strict” VOC and harmful substance testing. A good place to start your online searching would 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. There are a wide range of latex options included in the choices there and I believe that all of them compete well with the best in the industry in terms of their quality, value, service, and transparency.
Overall, I’ve tried to keep the responses more simple and direct, and I hope that all of this is helpful to you in your mattress search. If you come up with more specific questions, please let me know.
Phoenix