Hi jd,
Unfortunately your circumstances are well beyond the limits of complexity that can be easily dealt with on a forum or where I would be able to make any specific suggestions outside of the ones I’ve mentioned in my previous replies and there is no way for me to “diagnose” mattress issues when there are also complex medical issues involved because there are too many unique unknowns and variables involved that can affect how each person sleeps on a mattress in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) or any “symptoms” they experience.
I would also keep in mind that when there are complex health or physiological issues involved that there may be no perfect solution or mattress so “best possible” may be your most realistic expectation until the underlying physical cause of any symptoms you are experiencing can be healed or reduced.
In looking at the previous posts in the topic though there are a couple of posts that I haven’t linked previously that may be helpful …
There is more detailed information about the most common symptoms that people may experience when they sleep on a mattress and the most likely (although not the only) reasons for them in post #2 here.
There is also more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel”.
These posts are the “tools” that can help with the analysis, detective work, or trial and error that may be necessary to help you learn your body’s language and “translate” what your body is trying to tell you so you can make the types of changes that have the best chance of reducing or eliminating any “symptoms” you are experiencing.
Quite frankly I am also lost in the amount, details, and complexity of all the information you’ve provided and it would be helpful if you could provide a simplified recap of the layering combinations you’ve tried (listed from top to bottom in bold) and the specific “symptoms” you experienced on each combination and how they changed (became better or worse) relative to the layering combination you tried before it underneath each combination. The changes in your symptoms with each incremental change in layering combinations are really the only way to assess or guess at whether any changes you make from one combination to the next appear to be moving you in the right direction and to be able to see any “patterns” in your experiences that may help point to a combination that works as well as possible.
This sounds promising and if I was in your shoes I would probably pursue this type of zoning a little further perhaps with a little bit thicker layer of polyfoam and perhaps using more durable higher density polyfoam as well. I think you’ve read this already but there is more about zoning in post #11 here and the posts it links to that may also be helpful.
Again though … If you can provide more specifics about each layering combination you’ve tried and your symptoms on each of them and how they changed relative to the others then I may be able to see some patterns that may point to some additional options that may be worth trying.
Phoenix