Ruler2122, Welcome to the club of tinker’s and over-thinkers!
I have had some similar experiences trying to find a mattress that will support my hips yet give me pressure relief in the shoulder area. I have tried two latex mattresses without luck, so I will be very interested in what you decide on and how it works for you. Like you, I have been treated well by Denver Mattress.
Here is a link to one of my posts. You might keep an eye on it to see what I find out. As you can read, Phoenix is as surprised as I am at how these latex mattresses have broken down. I have no reason not to trust his experience and knowledge after spending a fair amount of time on this forum.
https://forum.mattressunderground.com/t/second-latex-mattress-gone-soft
I will follow this thread. Good luck to you and your aching back. Lew