Great report! It sounds like your son has a terrific head on his shoulders. Intent upon persevering, but level-headed and realistic enough to know that he has to explore options given the uncertainty of the rehabilitation he faces.
I'm assuming that his physical therapist is experienced in working with baseball shoulders. Once PT begins, it's as important that he not do more than his physical therapist expects as it is that he not do less than expected. This is not the sort of injury that benefits from extra work.
I'm sure that Ispeak for many of us when I say that we're all pulling really hard for a successful recovery!