Hi Ginger,
Do you sleep on your back, side, stomach?
Do your shoulders hurt from pressure sleeping on your side? Does it hurt when you’re laying there, or when you wake up?
By what you describe, it looks like the advice you got was based on the mattress is too firm, causing your shoulders not to sink in enough and getting pressure pain, but then when you softened it with 5" your hips sunk too far causing lower back pain. I’d guess they’re trying to find the happy medium by having 3" of comfort material getting progressively firmer to find the balance where your shoulders are comfortable without compromising the alignment for your lower back. Of course, that’s just my assumption from what you’ve written.
Does your lower back ever feel good? Can you run your hand under the small of your back, waist, while laying in bed?
I’d guess with 7" of super firm latex, you have plenty of support. That would definitely feel firm.
To soften is relatively easy… To soften and make yourself comfortable will be harder. To soften, just add toppers with a low idl (14-25 if latex), or memory foam, polyfoam, etc. As you e already done this, and experienced more pain, the trick is going to be to find the right toppers which give you suitable pressure relief and posture (2 of the P’s in Phoenix’s PPP).
If you’ve not already, you will want to read the post on how to evaluate a mattress for yourself:
It will probably be important, since this sounds like you have a few things going on.