If the prognosis is "tendonitis" you will be hunting in no time. If that is the case research shoulder stretches, that is what you will need to do to rid yourself of that.
Back when men did overhead presses, shoulder injuries were as rare as deer during deer season. Shoulder Chest and Back exercises will give your shoulder "girdles" balance, power, injury prevention, and stamina.
Bow weight, a weight that does not cause your muscles to recoil, retract, cinch, or compress. You should have a feeling of "circulation" at full draw, not contraction and stiffness.
That last part is probably the most important part of this post.
Good luck, and remember 40# @27 a 450g arrow kills most chest hit animals.