I disagree about this being a lack of respect problem. If someone backtalks you they lack respect. When someone tries to seriously injure you, it goes beyond that.

It sounds like either this horse isn't trained, or this horse has learned somewhere along the line that bolting is the thing to do. If he wasn't trained, well, now he has figured out that he can bolt and spook.. shit.

If he were mine, and he wasn't a superstar, and I would return him to the people I bought him from and get another horse.

If I was going to work through it, I wouldn't take him outside of the arena until he had been worked to the point where all he physically wanted to do was drag his body along at the slowest pace possible, even if this was after six months of groundwork. I wouldn't take him outside the arena until I could pick up contact and have him respond to it, because the instant that he bolted or spooked, he was going to get contact and a lot of it, and we wouldn't be playing that "OH, but I do stuff to AVOID contact" game. I wouldn't touch him with a ten foot pole unless I had good insurance, because this is a problem that can get people hurt.