Hi Awkward Sleeper,
These arenāt the specific density of the foam because it ranges from lower quality to reasonably good quality and a foam layer would have a specific density not a range but when you see a range of foam densities like this then itās safe (and wiser) to assume that at least some of the foam (if not all of it) is1.35 lb polyfoam which is a low quality material that I would avoid.
I would completely avoid using specs or layer thicknesses to choose a mattress unless you are a professional mattress designer and even then most people who design mattresses will tell you that in many cases they are surprised by what a mattress was āsupposed to feel likeā compared to what it actually feels like when they put all the layers together and test it in real life. The only specs that are important are the specs that indicate the quality of the materials in your mattress and I would use your own personal testing and experience to decide which mattress is the best āmatchā for you in terms of PPP.
Yes ā¦ lower quality/density foams are less durable but they are also less costly as well. I wouldnāt go below 1.5 lb density though even in low budget ranges (except perhaps for a thinner layer that is often quilted to the cover that is āaround an inch or soā of lower quality or unknown materials) and higher is better (see the guidelines here).
If there is mold in your box spring or foundation then I would get rid of it as soon as possible not only for heath reasons but so that it doesnāt spread to your mattress or put mold spores in the air.
Something like this or like this may be a good choice for a low budget platform bedframe that would be suitable for most mattresses and then all you need to focus on is a mattress to go on top of it.
Phoenix