WWYD? My horse kicked me in the ribs.

If he has pain issues, it could be that his escalating behavior is related to that, in conjunction with your lack of confidence. I would not rehome this horse. If I were you, and you feel you cannot find someone to help you with the issues on the ground, I would personally euthanize. It’s better to give them a kind ending, knowing you did all you could for them, so that they don’t meet a worse fate. Good luck OP.