Ok, I don't get it. Why is it that every time a horse does something wrong, people see it as being a "bad horse"?. It is seen as something with a behavioral problem to be fixed because that horse isn't fitting into our daily schedule. I have worked "problem horses" for years, I have been on plenty of rearing horses, but not once have I been on one that was rearing to be bad. I have been on horses that rear because of buddy issues, because they are confused, because they are in pain, because they don't respect the persons ability, the list goes on. Basically, it all points to the same thing, rearing is their way of telling you something, and its not subtle. Chances are, most horses show you all of the subtle signs, but no one notices, so, they take it up a notch. They do the same thing we do, ask, tell, demand! Once they get to the demand point, someone has obviously ignored the ask and tell.
Your first signs of a problem erupt long before the brunt force shows from the horse. In this case, the lack of focus and respect would show itself on the ground, in ways that many people wouldn't even pick up on. It would pop up further in the saddle, where the horse comes out with its own agenda. Remember, in a horses mind, that horse is always going to do whats best for it, first priority is safety, second is comfort. If the person can't provide this for the horse, then there is no way that the horse will give you all it can. Its not a matter of teaching the horse "don't do that or you will pay the consequences", its more a matter of showing them "I am the most capable of your protection and I have the tools to show you how to make yourself more physically comfortable". If the horses most secure place is with you, then these problems aren't going to be an issue.
Now, if I had the OPs horse, I would start on the ground and figure out where the initial hole is, because even if we were to fix the rearing problem through "cause and affect", the source of the problem would still be there and just erupt into another crater somewhere else. Without seeing the horse, we have no idea of knowing what this is stemming from. Given that the horse is running back to the barn, I would probably go to lack of attention from the horses part which also means not just lack of respect, but lack of trust in the person. I would build my way up from there.
If I were the OP, I would not sell the horse, but I would find professional help. I would want to be taught not just what the horse was doing wrong, but how I was influencing that and what I needed to change in myself to offer the horse what he needed. I always tell people, horses are always honest if you are willing to listen. Some horses will do what you want, ignoring any pain, just trying to please until they go lame. Some horses rebel, bucking, rearing, bolting, kicking, until they are labeled as difficult or dangerous, which they are neither, they are just the bold speakers of the horse world and refuse to compromise themselves.