Hi reflexbug,
I’m sorry to hear that the mattresses you chose didn’t work out as well as you hoped for.
I was looking through your earlier posts on the forum and at that time you were looking at softer memory foam mattresses similar to the cloud luxe so it’s possible that the soft version would have been a more suitable choice to keep your spine in good alignment over the course of the night (although of course latex is very different from memory foam in any firmness range). Don’t forget that in your lower weight range and side and back sleeping positions it’s very possible that firmer mattresses with firmer comfort layers may not provide the more even and contouring support you need to “fill in the gaps” in your body profile such as your waist and lower back.
Unfortunately it’s not possible to make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress. There are just too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort”, firmness, or PPP (Posture and alignment, Pressure relief, and your own Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
Having said that … post #12 here includes the list of the better online memory foam options I’m aware of (including Dreamfoam which is Brooklyn Bedding’s sister company).
Phoenix