Years ago now, I was referred to an orthopedic surgeon due to a shoulder injury - shooting a modern elephant rifle some 15,000 times did some non-reparable damage to my right shoulder. This probably was not as bad as yours, Dave. I had no rotator cuff damage, however the cartilage was smashed in my shoulder, on the front and on the back as well and I could not even pick up a coffee cup, let alone a cup of coffee. When my shoulder rotated forward out of joint one day as I reached behind me on the bed head for a Kleenex, my right shoulder dislocated- hurt like $#*! and locked, so I reached up with my left hand and pulled my arm back down - My family Dr. said "That's when you blew the cartilage on the back of your shoulder - anyway- that hurt some more.
Feeling very sorry for myself, I baby'd my shoulder for some time, had to 'carry my right hand in my right pocket as it was useless. I was so depressed, I sold my 14 bore rifle to a close friend. I could not even shoulder her, let alone shoot her.
After waiting for over 12 months to 'see' the orthpedic (socialist health care) surgeon, my cousin, a retiring MD climbed all over my case and said "work that shoulder, use it, you have to build up the muscle to support it, do not rely upon a surgeon to repair it - they seldom can help with a cartilage injury, but will try and then you could be in worse shape than ever".
Well, I did just as he said - after waiting another 6 months on the surgeon who never called even to acknowledge that I was his patient - took what Rick said to heart. It was a long road to recovery, but here I am, a number of years later, but for several of those (I got the 14 bore back) Ive been able to shoot her without having to wear a P.A.S.T. shoulder protector. i was able to shoot that rifle after about 6 o r8 months of exercising my shoulder, nothing special, but actually using my arm as best I could. The body is an intriguing machine and wants to run well - we need to let it.
I sincerely hope this gives you some form of white light at the end of a long recovery.
I wish you a compete recovery - it is possible. as long as i keep using my shoulder, it gets stronger all the time.