I am not a professional trainer, but here is my personal opinion and how I delt with my horse who was buddy sour.
First you have to understand that your horse is high strung and will freak out until he gets his way. He is TB after all, and mine is a mustang TB mix so I get your struggle :p
I realized after rescuing Ki that there was no fighting with her or reasoning with her. She will do anything thing to get her way even if it means hurting herself. So all I can do is let her do it and let her realize she is wrong.
She is very buddy sour. So the way I dealt with it is I let her run over to her friends, and the moment I got there I would make her keep moving. She automatically runs herself in circles because she is listening to me telling her to move, but I am letting her go where she wants instead of fighting her. After ten minutes of loping or trotting in circles she isn't having fun anymore and she wants to stop going in circles, so then she runs away from her friends. In response I stop commanding her to move.
I make the right thing easy and the wrong thing hard to the best of my ability.
I don't yank on her mouth, I don't kick her, I don't reprimand her. I just let her go where she wants and never let her stop moving. She realizes that her friends means work, and no friends means relaxation.
I let her think she is getting her way but she is not. After a week of taking this approach I was finally able to take her out on the trail.
So I would tie up your pony in a safe place near where ever you work your TB, and work his butt hard near the pony. If you have an arena or a fenced in field, tie the pony right outside of the fence so he is safe, and then work your TB on the the other side. Start in tight circles, make him tired. Let him decide when he wants to stop. He will tell you.
This will work, but it may take a while, especially with fit, high strung horses. But just have patience. It doesn't need to be a struggle.
And make sure you set him up for success. Don't take him out on the trail if you know he will act out.
As for how he acts when the pony is the one working...I would make sure he has his favorite treat before you go...like an uncle jimmys licky thing, or a bucket of beat pulp or some alphalfa or something. Or make sure he is in an open space like an arena or a field. Or, EVEN BETTER have someone work him in the round pen or on a lunge line while you ride off. Give him something to think about. Show him that pony is not his job, you are.
Those things may be a pain in the butt, but if you want to be a successful TB owner you're going to have to give him a lot of attention and time. Set him up for success, make him focus on you.
We need to l lunge their clingy butts into shape :p