I had the same issue with a bulldog grabbing my lurchers face. It took two of us to get the lurcher off it when he flipped. 30kg gripped on solid wasn't budging. He only let go to in the end to get a better grip. It wasn't pretty and now I don't trust my dog. Pain in the arse.
Bulldog had run out a few times but i ways managed to boot it away and my dog just wanted to get out the way. But that time he came out from behind a car.