Chains can be done in so many ways. Try changing the way you’ve put the chain on. Never pull them with the chain cause that’ll hurt their nose. Just tug once or twice. Carry a dressage whip on you when walking with your horse and if they ever enter your personal space just put the whip in between you and the horse or give them a small tap to tell them to back away from you
He probably just really didn’t like getting his mane pulled and is somewhat traumatized by it. Only do it in a stall or tied up outside. This happened with my horse and still happens sometimes (just her bolting out of the barn). First thing is that I would use a rope halter. This isn’t as painful as a chain but it puts pressure on their nose and it is easier to work with them. When he bolts out, go outside and get him and then immediately bring him into a ring or paddock that is not being used. Do 5 minutes or so of groundwork (backing up, walk/trot circles, etc.) this will establish that “I’m the boss, you have to listen to me”. Then bring him inside to the cross ties and praise him. Start at a short amount of time on the cross ties (2 minutes or so) and then bring him out. A little bit later do a minute or two more, and keep going up. As soon as he gets antsy or nervous bring him out before he gets the chance to bolt. Good luvk
I've had that happen to me before, either try to back them up to say I'm not putting up with your crap! And put them in their place. Then try it again and be firmer. You shouldn't let your horse run you over. Teach them some ground manners. If that doesn't work, just tack them up in their stalls. Some horses don't like cross ties.