Hi latexintheatx,
I’m sorry to hear about your husband’s issues. My first question would be if your husband has had an actual diagnosis of what you’ve described, as a true latex allergy is extremely rare (and can be quite dangerous). There’s more information in this thread about this. There is a good brief overview here about the three types of reactions that can be connected to latex.
Your comment is a perfect illustration of how there can be no “standard” definitions or consensus of opinions for firmness ratings and different manufacturers can rate their mattresses very differently than others so a mattress that one manufacturer rates as being a specific firmness could be rated very differently by another manufacturer. Different people can also have very different perceptions of softness compared to others as well and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions on how two mattresses compare in terms of firmness and some people may rate one mattress as being firmer than another and someone else may rate them the other way around, just as your opinion of what is “soft” can differ from what a manufacturer considers “soft”.
Some of the newer generation of high performance polyfoams, like the TitanFlex in the Brooklyn Bedding, are being made with more resilience but can still be made in quite plush ILDs. Of course, the overall comfort will be determined by the rest of the materials within the mattress. These softer HP polyfoams will hold shape better and be more resilient than lower density soft polyfoams. As you don’t like the feel of memory foam, something using, at least in the upper comfort layers, some of these newer softer HP polyfoams might be a good route to investigate.
Phoenix