I understand you, bro: 56 years old here and I also suffer from some back discomfort, although apparently not as pronounced as yours.
I don't know in what position you will have the cockpit adjusted, but I noticed more comfort by lying down more than I was at the beginning, with my feet practically at the height of the "derriere" and my back slightly reclined back, trying to imitate a position halfway between a GT and an F1. In addition to the improvement in my back, I have noticed that my feet swell less when I spend several hours sitting in the cockpit, since apparently before I had them too low relative to the seat. Now the only thing that hurts is my butt, but from spending so much time behind the wheel.
And regarding the computer problems... well, it seems that it's part of the experience, and I'm very afraid that the only solution to nip the problems in the bud would be to switch to playing on... (gasp!) console... In my case, since I only play Assetto Corsa I only have to worry about one game, which is already quite a task, by the way...
To try not to constantly ask about the same questions, I have become accustomed to saving in Favorites links to messages or videos of solutions to problems that arise, to take a look at them again if necessary...
And although it's cool to be in the latest fashion, other thing to avoid problems is follow the "if isn't broken, don't fix it" approach; I don't usually update applications that work well for me unless it's a necessity... For example, until recently I was using CSP version 0.1.79, and I have only updated it because it's almost mandatory for a lot of car mods that are appearing lately.
On a side note, I also tried installing Pure, but seeing how complicated is to adjust to make it look right, I went back to the old reliable Sol, which more or less gives me what I need. I don't know why I didn't follow my prerogative "if isn't broke..."