My only experience of a "broken" dog, was my Bull X.
Had him out lamping one night, he did too much and blew up, cost me around £1300 (not insured either!) to save his life, and he was no use for work after (I knew that would be the case after speaking to others)
At the time there was no question about having him PTS, and I definitely wouldn't have passed him on, after all who would want him?
I kept him as a pet, but the simple fact is, he was the worst pet ever, it was his body that was weak, not his drive, turned into the worst couple of years I've ever owned a dog (always had on