Hi all!
I agree with what gcoe has already mentioned. The shoulder complex is muscle-dependent and in case of bad positioning of the scapula, muscles attached to it are the ones to be treated mainly. Another aspect of your problem, arborvitae, is also recurrence of dislocation. It seems that repeated dislocation is not only a muscular but a capsuloligamentous problem as well. An unstable shoulder is pretty much what you suffer from -according to your problem's description- and in such cases a physiotherapy scheme including motor control retraining might not solve your problem 100%. A surgery might be indicated, according to your expectations and to certain criteria.
What you should do, in order to avoid future dislocations, is to visit an MD specialist of the shoulder or a physio specialist to give you a good assessment and guide you for treatment. It is very difficult to give you specific exercises without a clinical assessment here.
Hope I helped somehow.
ilias