Hey Dave,
Welcome to the community.
Congratulations on your nice health weight loss. I dropped to 260 (I am 6’) and now 220. For me the weight loss was needed for obvious heath reasons, sugar, cholesterol, you know the drill. Quite frankly, for me it did not affect my choice or comfort in firmness about my existing mattress and those I have been testing to do reviews on. For others, the heavier the sleeper, the more important the quality of the support layer and foundation becomes, although those characteristics are import all of the time.
I have recommended multiple folks to @ShovlinMattress in Fanwood, NJ. They have been able to customize a bedding system for a coworker specifically for a particular sized bed room requirement in their home and another MUGster (a subscriber here at TMU) to create a mattress that worked delightfully for his and her sleepers of different weights and sleeping positions. These folks are really old school in their approach with a combination of old school and modern materials to get the job done.
Depending on where you live in NJ, may direct where you might go. For example, Brielle Furniture in Sea Girt, NJ sells Shifman mattresses. Shifman have been around NJ for over a century and still make mattresses with all natural fibers and with classic traditional box spring combinations, these are truely 20-30 year mattresses. @ShovlinMattress is unique in that they can really personalize your mattress on the fly, and create a mattress that with proper maintenance, which is a key factor in longevity in addition to quality materials, can last you for more than a decade. They will also guide to the proper foundation and offer pillow suggestions which are key components for a well-rounded and correctly balanced mattress system.
If you are in northern New Jersey, you are just outside the city and there are a few worthy places that have the knowledge and experience to fit you with the right mattress, someone like @TheCleanBedroom.
I think you and your wife will find that mattress built with natural foams and fibers, tend to offer a cooler sleeping environment. Additionally, when I sleep on my left side (my body facing the middle of the mattress) I place a pillow adjacent to me, between me and my wife. It keeps my body in better alignment without additional hip and shoulder pressure. When I roll to my right shoulder, it is a bit more nuanced for me as I am literally on the edge of our king mattress (it has great edge support), so in order for me to keep my body aligned, I take the over hang of the comforter and tuck it between my knees to keep the knees from bumping into each other and it acts similar to placing a pillow between my knees, but this doesn’t move out of place when I am on my right side sleeping.
Hopefully, this provides you on the first step of your search, feel free to follow up with any questions or directly with some of the folks mentioned.
Maverick