Ouch, ouch... take care of that shoulder. ROtator cuffs ... you'd think "it's my arm, it's my legs I need for biking" but yea, communicate well with the docs and PTs aand don't assume it'll just get better.
Yea, you can't help but wonder "should I have been further out in the lane," "should I have been closer to the side?" Do you have a mirror?