Hi Logan,
No worries about the multiple posts. I think @NikkiTMU offered some great advice. The overall theme of what she was getting at is really a “less is more” concept. A lot of modern hybrids use thicker foam layers over a support core, and they just don’t perform the same way older style mattresses did.
What you’re dealing with is a mix of adaptation and how newer mattresses are built compared to what you had. Your 17 year old Sealy didn’t just feel good by chance. Over time it softened and broke in, especially in the top layers, and created a natural cradle, which you adapted to, but eventually became too much. As a lighter side sleeper, that likely took pressure off your ribs and side in a way that felt normal to you. Your body adjusted to that gradually without you noticing. Much like looking in the mirror every day for 17 years, you don’t see much change until you compare an old photo to one from today and realize the difference is actually pretty significant.
Now with newer mattresses, you’re going back to materials that are sometimes more resilient and less broken in. A lot of what you tried from Helix, Purple, and Tempur-Pedic uses thicker and sometimes denser foam layers depending on the model. Some brands today also use lower quality foams that feel good at first, but don’t hold up over time, which can lead to aches and pains as they change. Even when labeled soft, many are designed to hold their shape longer and do not contour with your body as needed. At your weight, you’re likely not sinking in enough to fully engage those layers, so you end up getting pressure on your ribs and side after a short time. That “feels fine at first then gets hard” feeling is usually pressure buildup, not lack of support. Out of the three, Helix is probably the closest to something that could have worked. Purple uses a grid material that is more gimmicky and doesn’t really give that traditional conforming feel. Tempur material is very specific (viscoelastic temperature sensitive memory), nothing traditional about it, and while it works for some people, a lot of its popularity comes from heavy marketing and advertising rather than it being a universal fit.
Where I think you’re on the right track is looking at simpler, more traditional builds. Older style mattresses were usually coils with thinner foam layers on top, not an overabundance of dense material stacked up. That which offers a bit of spring and easier contouring without that pushback feeling is going to provide you with the familiar feel that you are used to. Something like the @DLX Classic Hybrid or options from @BeloitMattress and @ShovlinMattress offer mattresses that are closer to that style. They still use better quality foams and natural fibers (unlike some legacy brands who have lowered their foam standards to meet corporate objectives), just not too much of it, so you get some give without feeling stuck on top. More of a springy, conforming feel.
On the higher end, a couple of the brands like @plankandcoil and @thecleanbedroom offer focus more on traditional construction with higher quality components. They’re not trying to pack in as much foam as possible like a lot of big brands today. The feel is more breathable, a bit springy, and easier to conform to your shape without creating pressure points.
Two other things that matter here are your pillow and your foundation. Your old mattress definitely had some softening or body impressions, which changes how your pillow aligns your neck and spine. On a newer, flatter surface, that same pillow can throw things off. Also make sure your foundation has little to no flex. A lot of newer mattresses are designed for a solid base, and any give underneath can make pressure issues worse.
Overall, I would not go firmer. That will likely make the rib and side pain worse. You want something that conforms more easily, but not by adding a lot of dense foam. A simpler coil based mattress with moderate, good quality comfort layers and a bit of spring is probably closer to what your body got used to.
I’m not suggesting there are no BiB options that could work, because there are. But looking at more traditional designs will probably get you closer. Materials with a lot of pushback, like some latex builds, even though they are durable, may not give you the feel you’re after. Natural fiber mattresses can feel a bit dense at first, but they tend to relax and conform over time. That natural fiber contouring can sometimes be mistaken for sagging or severe body impressions, but it’s often just the material doing its job. I had this effect with my 3" organic wool topper. When we would wake up in the morning, the mattress looked a bit off, like it was sagging like crazy, but in reality, the topper was doing it’s job and simply cradling our body and contouring in alignment to our shapes. Natural fibers do not bounce back like foam (although horsehair does this a bit better) so you see the natural body impression it creates.
Hopefully this gives you a clearer direction on what to look for.
Maverick