Have read now through your introduction... Have you thought of gelding your boy since he's limiting your ability to go on trail rides? It really would help his demeanor around other horses, at any age.
I used to have an Arab stallion, but he was a really easy one around other horses. He'd always been shown and was socialized that way. Still, I used to smear a little Vicks Vapor Rub in his nose at horse shows, it kept his concentration a little more focused if he couldn't smell anything but mentholatum ;~D
Yes I do want to geld him, but the decision is not just mine, and he has a testicle that has not come down, so there are special considerations, and costs. He's still a happy camper though. But his falling in love with a little bull was not my intent.