Hi zman1.
I appreciate you sharing your sleep stats and the results of your trials and errors with finding the correct head elevation and the best pillow for it which can be sometimes as difficult as finding a mattress. It sounds like you’ve managed to solve the “riddle” of your neck and what you need support-wise in that respect.
Changing the mattress may require that you also change the pillow so the leg work that you already did will come in handy if you need to make adjustments. Pillows are a very personal choice and different people will have very different pillow preferences and the perception of firm or soft for each individual are also different. There is much information about this in the pillow topic to help find a pillow that is the best “match” for you and the mattress you end up buying…
Because you have a larger frame and higher BMI, I’d first focus on the durability and useful life of the materials & components in your mattress. Because no materials will last as long with much higher weights the quality and durability of the materials and components are even more important than normal. I would base your choices as much as possible on your own personal testing Post #3 here~ has more information and suggestions about heavier weights that is worth reading.
While the weak link of a mattress is generally in the upper layers … with you also sleeping on your side mostly the depth of compression would go a little deeper than most and the feel, performance, and durability of the middle and even deeper layers would likely be more important. In these cases, it would be more important to make sure that the support layers are higher density or a more durable material or that the latex on top of the mattress is thicker or has two layers of latex instead of one
As you “are not going” for any memory foam in your mattress that leaves you with Polyfoam and Latex and/or fibers. Latex is a durable material in general but if you’re considering mattresses made of poly foam, if the mattress is one-sided then I would look for 2.0 lb per cubic foot density or higher. If the mattress is two sided then I would use a minimum foam density of 1.8 lbs per cubic foot or higher.
As a side sleeper, there are deeper gaps to “fill in” to spread your weight out on the mattress when you are sleeping and you need a deeper cradle to relieve pressure so the gaps are filled in and help spread the weight over the mattress.
In general, a good starting point for a good comfort layer for a side sleeper is 3" and then depending on weight, body shape, preferences, and the firmness of the support layers, to go up from there if needed. Your hip/glute/leg discomfort makes me question the weight differential between your hips and legs how much your hips sink in as opposed to your legs, the position of your legs, and if there is any twisting involved.
Making any specific recommendations for mattresses can be tricky and it is nearly impossible to diagnose pain issues through a forum as only you can feel what you feel on a mattress, but because of your stats and specifics, you would be better served by talking with a manufacturer that focuses on matching the mattress with the sleeper. It may be worth checking out FloBeds. They offer an option for “big and tall sleepers” that you may find interesting. They also have customized horizontal zoning for individuals with different than average sleeping profiles and needs. You can reach out to them directly with your stats, preferences, and questions and they can guide you towards the best fit from their options.
You may also want to reach out to Arizona Premium Mattress, Seep EZ, Latex Mattress Company or Foam Sweet Foam.
Ultimately, any single one of our Trusted Members will be transparent about their mattress components and will be able to answer any questions you have about the products they offer, and whether they feel they have an option that would be a good fit.
I hope this helps get you off on the right foot. Please keep me posted with your progress.
Phoenix