Only you and your surgeon can decide when it is right for you. Please be cautious not to reinjure that shoulder while diving or any other activity that stresses that joint. My injury was a single torn rotator muscle, down time about 2 months but even 3 years later, movements that isolate that particular muscle are weak. I have learned to adapt and rarely have any problems now. When I first returned to diving I remember having trouble lifting objects (my camera/fins) to the deck crew when in the water and needing to put the bad shoulder in the BCD first. Climbing the ladder was less a concern then holding on to the boat to remove fins. Please don't use the injured shoulder for this. But with the extensive damage that you had you must have already adapted your diving for a bad shoulder at least to some extent?