Hi BrentinKC,
You are probably lucky to get 5 years for a euro pillowtop from any major brand before the lower quality foams in the pillowtop softened to a point where you lost good support and alignment. Your lighter weights probably helped it to last a little longer.
Since you’re posting in this thread I’m hoping that you’ve read the various links in the first post about avoiding chain stores and major brands so I wouldn’t recommend either the Tempurpedic (generally better quality but poor value compared to other similar memory foam mattresses) or the iComfort line (lower quality and also poor value). You can see my thoughts about the Tempurpedic line in post #10 here and the iComfort line in post #11 here.
Many smaller or local independent manufacturers sold factory direct or through better sleep shops would make high quality memory foam mattresses that were similar quality but significantly better value. Personal testing along with buying from a retailer that disclosed the type and quality of the layers in their mattress would lead to a much better choice.
Some of the better options and possibilities I’m aware of in the Kansas City area are in post #2 here.
Most of the rest of your questions (such as alternative types of mattresses, ideas about the type of layering that would be suitable for your weight and sleeping positions, and what to look for and what to avoid) would be answered in the links included in the first post of this thread which is probably the best place to start before you begin to look for or start testing mattresses.
Phoenix