Wow, William! My Jaw dropped when I read all that you’ve been through! Holy cow! It’s totally different for me. I have played professionally and taught for over 30 years. I am almost 60 and last year, I found out I had an injured rotary cuff, on the left side. I hadn’t fallen or anything, but boy did it hurt. All the docs and therapists were certain it was a result of years of playing professionally. Made me mad to think about it. If I play too long now, or even use that arm for other repeated motions like typing, I get a little reminder that more pain is coming if I don’t give it a rest.
I think part of your pain remedy is that you are keeping yourself busy with something you really enjoy and so it provides a distraction from the pains you would normally notice if you were sitting and dwelling on them. I say, if it gives you relief from pain, that’s a plus! Lots of players injure themselves with bad positioning and posture over years and years. So, like any athlete, warm up, stretch out, work it, cool down, frequent rests is key. Sometimes if you have a goal of practicing an hour a day, you might break it up to four sessions of 15 minutes, with stretches and warm ups each time.