I've also suffered for years with RC troubles, and after seeing a number of PT experts, I've finally gotten relief with chiropractic adjustment and coordinated PT. I've also been able to get back to lifting. A few things that my PT said that you might want to consider:
1. Bench Presses: Don't. Just don't. I know, you want to do them, so did I. Eventually you can probably work in flys to your routine like I did, but bench presses put an enormous load on the shoulder.
2. Military Presses - My PT said not to these either. Basically he said that anytime you are lifting above your shoulder level, you're also putting a lot of stress on your shoulder. Instead he recommended this dumbbell exercise: Standing, start with your arms at your side. Lift the dumbbells with your elbow straight until your arms are parallel with the floor, then lower. You should raise your arms in a plane about 45 degrees in from your side, so that from a birds eye view, at the high point of your motion, it would look like a 90 degree "V" with your body at the vertex.
PT-prescribed workout routine: After your pain subsides a bit, have your PT put together a workout routine for you that will protect your shoulder. If they are reluctant to, find another PT. (I've noticed a wide range of skill sets in PT's.) And I'd recommend to try some more PT's before you even consider surgery. Good luck.