Hello Thomas. Your rating will largely depend on your range of motion. Being deemed fit or unfit to continue service will depend on other factors, such as being able to conduct the operations of your job. If your shoulder is preventing you to from doing PT, I would recommend getting a profile from the doctor stating what your limitations are (no push ups, no running....whatever you can't do). Some commands will try to administratively discharge you based on failing PT, but if you have a profile on your physical limitations, this will give the doctors something to work with as far as starting an MEB, if they feel you will not get better. Be prepared for a long process, more conservative treatment...ice and stretch at physical therapy....and then maybe your doctor will start an MEB. Or, since you have already done many treatment options, they may just go straight for the MEB, who knows. Everyone's case is different.
I was rated by the service as 20% for my shoulder surgery, but the VA rated me higher at 30% because my range of motions were different. After the surgery the range of motion was high enough to warrant a 20% rating. A few months later after discharge, my shoulder injury started to get worse again. When I conducted range of motion tests with the VA doctors, it was much lower, and therefore warranted a higher rating from the VA. I hope this helps.