He isn't slowing down because he is evasive. You aren't asking him to slow down, you're letting him run over those jumps, slamming him in the mouth, and not trying to train him. Jumping and barrels are fun, but there is nothing right going on in that video. Why do you keep slamming him in the mouth like that? At this point, I'm not even going to ramble about jumping in a curb bit, but to jerk on his mouth like that is absurd. It is not teaching him anything.
I don't get why you post videos of you and your horse, then get all POed when we tell you your horse has giant massive gaps in his training. It is not rude. It is not mean. It is honesty. The ONLY reason your horse is rushing around like a bat out of hell is because of poor/incomplete training. I have ridden OTTB horses, barrel horses, OTTQHs and they ALL knew how to slow and stop and be soft. I don't care if he was trained saddleseat or was a roadster -- That isn't the reason he's running around unbalanced and avoiding your hands.