Ah, mate, I appreciate your opinion. Your thoughts are well thought out and lucid, helpful, and said in a friendly, agreeable tone.
And the thing is, I can't settle for that. If I am going to be in tennis, I need to be the greatest. I cannot be happy being a linesperson, I cannot be happy being the guy giving lessons to 40 year old housewives. I've worked at more than one tennis shop, I can't just sit there and watch people play all day while I'm there lusting for the game in the pro shop. I cannot be happy not being the best. When I am among tennis folk, when I am discussing, I feel as though they don't respect my opinion because they've coached this guy and that guy and this other guy used to train with so and so and I haven't. When this happens, and it does often, the feeling I get when confronted with this, a fire explodes in my eyes and passion runs through my blood to prove them wrong.
Nothing else in life gives me this same rush, and trust me, I've looked around.
Millions of guys have called it quits cause of injury, but I won't, and I can't. I've tried it even, come up with every excuse, but I couldn't live with myself, couldn't look at myself in the mirror knowing that I could still play and not giving it a shot.
I understand your train of thought here. Like your passion for the game and the desire to be the best is a great quality. You have to watch out that it doesn't destroy your arm though. Listen to your doctors, or at the very least to your body. I am also a person who has always played through injuries (albeit not as severe as yours) and I can tell you, at 30, you will start noticing them outside of the tenniscourt aswell..
Because I recognize, and applaud your stubbornness in this, I know that telling you to stop won't help. My advise would be to have a long, serious talk with a doctor about this. Ask him what are your chances of damaging your shoulder for good, and your chances of being able to play free-of-injury. Base your decision on this. Even though I like fighters who don't give up, there is honour in knowing when to quit too. I'd hate to see you permanently injured.
Good luck mate, I really hope you will be able to play!