A breaker bar does not slip over a wrench. A breaker bar is a specific tool. It is basically a solid metal bar with an end that accepts a 3/8 in or 1/2 in socket.
Slipping a pipe or anything else over a wrench to increase leverage is NOT the correct way to break a bolt or nut loose.
Sorry to hear that the head of the bolt is ruined.
Good luck getting it off now.