Hi Rob,
Thanks for the kind words 
While I am not a particularly “sensitive” person … I have also experienced the results of memory foam offgassing and it certainly isn’t pleasant and in some cases can be quite frightening for those who are more sensitive or affected more than most. In my own case, in addition to the symptoms you describe it also led to muscle fatigue. The mattress industry today is filled with misinformation and I personally believe that the “best” first step is to find an outlet that has the knowledge and can be trusted to give good information and guidance. These are generally factory direct outlets or better sleep shops that carry local or alternative brands. There are still quite a few in most areas of the country but they tend to get drowned out in the noise of advertising and misleading and contradictory claims. Post #2 here should give you some better options in the South Florida area to include in your research (and I would start with a phone conversation to make sure they made or carried mattresses that fit your criteria) in case some of these haven’t shown up on your radar.
If you are in a different part of South Florida … let me know and I’ll take a look to see if there are other that are near you that I may know of.
There are some weight/height/body shape guidelines here and some guidelines for different sleeping positions here but I am a big believer in local testing because there are so many variables in what makes a particular mattress work well for some but not for others who may otherwise be very similar that these are only guidelines rather than recommendations. These variables may be slight differences in body shape, sleeping positions and also the many variables in the materials and construction of different mattresses which can make a significant difference in how a mattress feels and performs for any particular person.
Once you have a reference point … then if there is not good value locally it also can make an online purchase much more accurate for those who choose to go in that direction. Some of the members of the site that make good quality and value mattresses and who have the skill and knowledge to provide great guidance over the phone for those who choose to go in this direction are in post #21 here. They are also a good “value” reference point for a local purchase and many of them use either natural or organic materials in their mattresses. One is probably the greenest mattress manufacturer in the country and they actually have zero energy bills using solar, geothermal and wind power that they generate.
As you know, there is also quite a difference between “organic”, “natural” and “green” and there are many outlets that take full advantage of all the confusion about these terms. All the manufacturers you listed (OMI, Savvy Rest, and GreenSleep) make high quality and natural products (there are no actual organic latex mattresses although many manufacturers use either organic or natural materials in the different component parts of their mattresses). All of these though carry a significant premium for their “organic” focus in spite of their quality when you compare them to similar mattresses that also use similar or even the same natural or organic materials but have much better value (including several on the online list I mentioned). The key is to make sure that the ingredients that are in the mattresses you are considering are natural (or organic if that is your preference) and that the manufacturer is open about the materials they use. In many cases the word “organic” can mean “more expensive” than other manufacturers who use the same materials but don’t have the same focus on the organic market and just use these materials because they believe they are better quality.
The only “mathematical analysis” or algorithm that I know of is a proprietary one that is used by Custom Sleep Design that they are using quite successfully to make recommendations (also on the online list). For the most part … manufacturers use a set of standard guidelines similar to the ones I mentioned (or their own) and then use their experience, knowledge, and intuition and your feedback with local testing to make any adjustments that may work better for you. Each will also have their preferences of design and ideas as well that they are more comfortable working with as well. In the end … it’s all about PPP (Pressure relief, Posture and alignment, and Preferences) and there are usually several pathways in terms of materials, layering, and design to get to the same or a similar outcome.
The first thing I would do is to decide if the reason you are looking at organic is more about safety or if it is about a philosophical preference. If it is more about safety … then this opens up possibilities of materials that are “safe” but not as natural or organic. If it is about a preference for natural or organic for it’s own sake … then this too would help you eliminate “non natural” choices and focus on the ones that are natural or organic only. Either way you have some good choices.
Hope this helps but if I’ve missed anything feel free to post with more questions.
Phoenix