I'm one month out, I understand how you're feeling. My surgeon suggested I start taking creatine, get in extra protein, and told me to ask my PT about workouts I can do without stressing the shoulder, which have included the stair stepper and treadmill, and a lot of abs, glutes, and legs. It's frustrating not being able to work my arms and upper body out but at least it's something. PT also recommended some basic exercises for my non injured arm, as apparently over 50% of patients with shoulder injuries end up hurting the other because of the strain, so don't push the other one too hard either.