So, I am just curious, forgive me if it sounds nosy, but how did you injure your shoulder twice? I got the impression that you are younger than me (moi- 44). I know the terrible mechanics of my serve probably got me into this and developing a real big loop on forehand for topspin only exacerbated it. And then what finished me off was continuing to play with the injury and not resting. Just wondering how it happened, you're fully recovered now I take it?
I was 16 when I first injured my shoulder. While the MRI showed a partially torn supraspinatus. My surgeon was not convinced of the findings and even if there was indeed a tear, it was extremely small. He was optimistic that my athletic build and young age, coupled with physical therapy and rest would heal the shoulder. After 6 months of physical therapy, I demonstrated an increase in strength and etc., but I still could not serve due to aches and pains. I then pushed the conservative surgeon into arthoscopic surgery so we can see the shoulder directly, and fix it. My supraspinatus was indeed healthy and not torn, but I had an inflamed bursa, bone spurs, and he proceeded with the subacrominal decompression. Rehab, rest, and back to tennis.
Then at 22, I injured my shoulder for the 2nd time. I was playing basketball and my arm was caught by two defender attempting to block my lay-up. Nothing dirty, just an accident and I was at the wrong place at the wrong time. I suffered a partially torn supraspinatus (for real this time), and a partially torn posterior labrum. Rehab, rest, and back to tennis.
I just turned 27 and I don't seem to be suffering from any significant ill-effect of those surgeries. ROM is full except for interior rotation, I have ~90-95% of interior rotation? You can easily check it by attempting to run your hand up your spine.
Strength wise, both arms are equal and I'm benching 200lbs x 10reps. If I'm using dumbells, 80lbs x 10reps on each arm. I'm about 5'8, 140lbs. That should give you an idea of my strength.
I'm going to say something about working out. I try my best to make sure my joints' stabilizers are not overwhelmed by the larger muscle groups pulling on the joint itself. I do stay away from MANY shoulder-hazardous exercises at the gym. For example, I don't do "dips". It's one of the stupidest, showboat-est exercises out there. It works out the triceps but at the same time, it puts the shoulders at an awkward position. There are better and safer exercises for triceps. I also don't do inclined benching, it exposes and makes the bicep tendon vulnerable. Basically, I stay away anything that puts the shoulder in awkward positions and unnecessary loads. Also, for the external/internal rotation exercises which you'll be doing in about a month or two, I do not exceed 10lbs and I always go for high reps, up to 20 reps/set. You need to understand the rotator cuff is made up of muscles designed to
stabilize the joint when the larger muscles groups are utilized.
As a stabilizer, the rotator cuff was never evolved to bear short, instantaneous blunt forces. So there's no need to do your external/internal rotation exercises on 50lbs. I'll pick a harmonious joint over an unbalanced joint any day. I am still doing the rehab exercises as a maintenance routine. I recommend you to do the same too, and keep the weight low and high repetition.
Tennis wise, there's no restriction. I almost always play singles. Average playing time is about 3 hours, with the occasional 5 hours sessions. Now I have more free time than ever, I work on my serves during the day, and play at night.
Serves about 150-200 balls, come home, ice it once, then go out at night and play for several hours, come home and ice it again. I play about 5 or 6 days a week.
You can see my racquet and modifications in the signature. I do play with natural gut and I am in the process of experimenting with several polys in the crosses.
Yikes, I thought that was the case. In my mind two weeks was the magic number whereby I would suddenly be able to lift my arm ok. 
