I assume you know how to train the dogs.....horses are not dogs.
Horses learn on the RELEASE of pressure. That means that if he does something wrong, like spooking and rearing, and you let go of the lead rope, then you just taught him to DO that. Similar to calling a dog to you, then yelling at it...then expecting it to come when called.
Arabians are generally quite sensitive, and that means it does not take much to move them, teach them good things, etc., they are the standard Poodles and Golden Retreivers of the horse world. Trust to them is a person who is rock solid when they are quivering. Same as with a dog, DO NOT pet or console a scared horse. You are then rewarding scaredness.
Your gelding is adorable, and Arabians are usually slower growing, anddo not mature until late, so I think he has a bit of growing to do.