Hi Andy,
Royal bedding doesn’t have an “up to date” website (he’s working on it) and does offer memory foam in different densities as well as other models that are not listed. They are a family manufacturer and he is a great guy to talk to. “At this point” he doesn’t offer latex but he does carry memory foam (from glideaway) and his own two sided mattresses. (NOTE added later: He now makes a high quality two sided all latex mattress)
Also near huntsville … there is a regional manufacturer who offers a variety of mattresses called Denver Mattress. They have many outlets in several states so the level of knowledge may not be “consistent” from outlet to outlet so make sure you are dealing with someone who knows the layering of the mattresses you are testing if you go there.
If these don’t offer what you are looking for … let me know and I will take a look at some retail outlets in your area that offer “non major brand” mattresses that may be worth visiting for “testing purposes”. A quick look says there are at least one or two of these.
ADDED: Post #2 here has more Huntsville options.
From your “stats” and description … it is clearly important to find a mattress that offers both pressure relief and support. If you do go with memory foam … which is not always the best idea with back issues … then I would certainly choose the thinnest memory memory foam layering possible (for your pressure relief needs) using high quality memory foam and make sure that the support system underneath it kept both of you in alignment. A side to side “split construction” may also be an option if your needs are too different (which testing will confirm).
An exceptionally high quality split king mattress using the best materials and layering should still come in at well under $3000 (at the top end) and significantly less than this is also easily possible for very high quality mattresses using the resources on this site depending on the choices of materials and construction that are “best” for you and your circumstances.
In terms of an adjustable bed … the best value I have seen is here (where I bought mine). You could either use this as a reference point or for an actual purchase. I would also be a little careful using an elevated position (either head or foot) with side or stomach sleeping as it would be more suitable for most people when they are sleeping on their back.
Keep the questions coming if you need more options or if your research on this site and others needs any clarifications 
Phoenix