Everyone else has pretty much already voiced it.

If you're scared of him, you should sell him. The only thing you can do is be honest with people who come to look at him. Tell them what you know, and hope that he goes to a good home and not somewhere that is just going to dump him.

If you can keep him and gain your confidence back, a few years down the road this might all just be a distant memory. Horses can change.

Either way, good luck!