I don't know man... 160 is only 2 hours. Time to fix someone else's mistake (especially if it truly took a torch), install new caliper, bleed system. It doesn't sound too outrageous to me.
I see where you're coming from, and I am almost always on the customer's side, and I feel for the kid. Good luck.
PS, if I had torches, I'd tell you to head over here. Although I also never had to use a torch (our shop didn't even have one).
PSS, sorry, I thought you meant he snapped off the bolt. He just needs a bolt broken loose?
Final PS - what was the car doing in the first place - that made them say it needed both rear calipers (which sounds like a parts hanger shop to begin with).