Hi missingmyoldmattress.
Welcome to our Mattress Forum. 
I’m sorry that the mattress you loved is no longer available and that your replacement isn’t giving you the proper support and pressure relief you need. You’re not the first looking to replace a mattress that is no longer in production. You might find it helpful to peruse post #9 here which describes several ways that one mattress can “match” or “approximate” another one.
There are also several factors that can affect how soft or firm a mattress (or an individual layer) feels besides just the exact specs, density, and ILD of the foam used (see post #4 here for more information )
The best you can hope for in such an endeavor is to find something “in the range”, but only your own careful personal testing along with several detailed conversations with an experienced and knowledgeable manufacturer/retailer may have any chance to get you a little closer to a mattress that replicates your sleeping experience of your preferred mattress.
NikkiTMU