About your right thumb, Dustin. Your problem from my understanding is that you use Green joint in your right thumb to play bass note(from my picture in previous post). And that's wrong, the correct joint is Red. But now you already have bad habit and it's hard to get rid of.
I have a idea, and it's from my experience. I used to have weak right thumb due to using wrong technique. So I borrowed an acoustic guitar and because its bass strings are made of steel ,it's harder than classical guitar to pluck. I tried to brute force it, playing as loud as possible. My goal was to erase bad habit, change from using green joint to red joint.
For a week, I practiced my right thumb: using a cloth to damp the sound and watching Game of thrones at the same time. Happy practice happy life