The Princess and the Pea story - Need to find a "just right" mattress

Hello, I’m extremely new to this forum and I have been lurking for the past few weeks. I’ve been suffering endlessly after moving with my SO and subsequently inheriting their mattress - A well-worn, uncomfortably firm queen-sized Sleepy’s Relax innerspring mattress. I ordered a Viscosoft 3 in high density foam “cooling” mattress topper to try and find a relatively quick fix, but it is too soft for me, and my partner and I both sweat through the night on memory foam (even though it was touted as cooling and gel-infused).

I now have to dive into the very large and confusing world of mattress shopping, and so far it’s been a bust. I’ve spend countless hours trying to research the “perfect” mattress online, until I learned that most bed-in-the-box websites have sketchy reviews and some brands are manufactured by the same parent company that use sub-par materials and coils (I’m looking at you, Nest ASH). I tried out brick and mortar stores like Mattress Firm and was tempted to purchase a clearance Serta iSeries 1000 medium hybrid, until I read that I should avoid the questionable quality and mark-up of the “S” brands. So now I’m stuck.

I have to accommodate a 6’4" 200lbs hot sleeper, usually a back and side sleeper (who admits they can sleep on pretty much anything). I am a 5’9" 145lbs back/side sleeper. I do sleep a bit hot as well, and I suffer from chronic tension/muscle spasms in my neck, back, and shoulders from fibromyalgia. I am also quite restless as well, and tend to wake up multiple times a night (although hoping a better mattress could fix most of my issues). I tend to like my mattresses on the softer side, but not so soft that I sink into the material and get “stuck”, so possibly around a medium to medium-plush firmness.

I know that no mattress will be the PERFECT fit, because meeting all my criteria is close to impossible. I’ve been looking at hybrids due to the combination of some motion isolation, some pressure relief, not sleeping as hot as purely memory foam mattresses, and long-term durability (including edge support). I’m looking for king mattresses, although I can be swayed to a split king where I get a more supportive mattress and my SO gets a decent but not top-of-the-line mattress (they confirmed this was an option). Ideally, my maximum budget is ~$1700, because this will be my first-ever solo mattress purchase. It’s a significant chunk of my savings, so I want to find a mattress that can hold up reasonably well against issues I’ve been seeing for BIB mattresses and some big “S” brands like premature sagging, pitting, and edge breakdown.

In other words, HELP!