Hi hoyt,
The first place I would start your research is post #1 here which has all the basic information, steps, and guidelines that can help you make the best choices. it also includes a link to mattress firmness/comfort levels in post #2 here which links to some of the pages that talk about mattress theory and design but these are only generic and not specific to any particular person. In most cases it’s usually best to test for the design that works best for you regardless of the ILD’s of the layers because your body will tell you what works best for you much more than trying to choose a mattress based on specs or whether you know the ILD of the layers.
Some of the better options or possibilities in the West Palm Beach, FL area are listed in post #2 here which would be a good starting point and of course if none of them made a mattress that matched your criteria then the online members listed here can be a great option as well.
Phoenix