I had my one arm from the shoulder down tore apart to deal with cancer a while back. While I still have use of the hand, mobility of the shoulder is a problem.
Really I found diving SUPER helpful as it gave me a weightless environment to do physio in, not to mention was a welcome distraction. So far I have almost doubled my range of montion, something I attribute mostly to diving.
Just take the time to look at how you have rigged the gear. I swapped shoulder dump/inflators and switched the side that my reg's come of the tank. Totally backwards I know, but it works for me. Makes me look like a mirror image to people when they watch me in the water.
Use good retractors. It will keep everything imporatant centered. Get a good buddy who will help you when needed and good luck.