Yeah, getting it off the bb without further damage could be tricky. If you can get the drive side cup out, great, but that's a PITA even when the bb is out. If you can find a shop locally with the thread repair tool, it should be possible to tap it in place without removing the bb. Or if the tool isn't available locally, maybe another shop would loan it out? Seems safer to ship the tool than trying to disassemble so you can ship the crank arm.