Boy, your first post sounds very eerily similar to what happened to me , after a shoulder surgery repair. Mine came from a motorcycle accident, where I took the brunt of the impact on my low back, dislocated my right shoulder ( which was put back into place during the ambulance ride-NOT the way to have your shoulder relocated into it's socket!). Anyway, almost two years later, I went in to surgery for a anterior shoulder reconstruction and was placed in an immobilizing splint for three months, and sent for physical therapy , where I also developed a frozen shoulder and the added complication of Reflex Sympathetic Dystrophy or as it's called now Complex Regional Pain Syndrome.
It sounds like you may be experiencing similar problems.
The best thing that I can suggest is to get yourself into see a good pain management doctor who is familiar with treating RSD/CRPS in the biggest hospital in your area ( preferably in a large city or teaching hospital).
I also lost the use of my entire arm, shoulder, hand and fingers over the 7 years that I dealt with RSD and the frozen shoulder, atrophy of all of my arm, hand, fingers and shoulder, but I have managed to regain much of what I lost, albeit during the time, it was excructiatingly painful but worth it in the end.
Hang in there, getting the pain under better control will allow you to participate fully in physical therapy so that you can stop the progression of the atrophy and regain the use of that arm. You don't want to loose the use of it. Don't give up.