Hi baddog,
You are really the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components would be the best “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own careful testing or personal experience … hopefully using the testing guidelines in the tutorial post (see mattress firmness/comfort levels in post #2 here).
Having said that … the mattress you described would be softer overall than most people in your weight range would normally do best with “on average” and in particular the thickness and softness of the top two layers may be more risky in terms of your alignment than firmer layers but your own careful testing and personal experience always “trumps” theory because not everyone fits inside the averages.
Latex is the most durable of all the foam materials (polyfoam, memory foam, latex foam) and it would be more durable than other materials in the same firmness range but it’s also true that softer layers will be less durable than firmer layers of the same material (with higher weight ranges especially) because the amount of deflection of a foam layer is what causes it to soften and break down. In very general terms I would be more concerned about the suitability and the durability of the top two layers and with the softness of the mattress overall than I would be concerned with the durability of the bottom layer although most people in your weight range would probably also do better in terms of PPP with a firmer support core as well.
Their ILD ratings also seem to be out of the range that most people would call soft, medium firm, or firm so I’m not sure how accurate their ILD numbers really are or how the ILD was tested (see post #2 here). If their “word ratings” are more accurate than their ILD numbers then “in theory” the mattress would be more suitable for more people in your weight range based on “averages”.
There is more about the many variables that can affect the durability and useful life of a mattress in post #4 here and the posts it links to.
Phoenix