I agree with what most others have already said re: sending the horse to a trainer for a while. Whether you keep or sell him, ultimately, he’s going to need more training. I also agree that this horse does NOT sound like a beginner or kid-safe horse; he clearly needs more miles and confidence.
I will chime in on the heaves (Equine Asthma) diagnosis. Unless your horse is severely affected, there is no reason to think that he can’t be a performance horse. With proper management, most EA horses continue in moderate and even high-level careers. My EA horse competed in the 2’6" and 3’ hunters for years after his diagnosis, completely medication free. 24/7 turnout and NO round bales are the first steps; soaking his hay may be necessary. Always feed him at chest height or lower, and take it easy on him when temperatures are very high or very low.
