Empathizing with you...
First off, welcome to the forum! I'm relatively new here also. I bought a horse (a Criollo) down here in Cancun, where I am currently working. He had won first place 25 times in jumping. Unfortunately, he became sick with a lung infection and was pretty much ignored and abandoned. Those at the ranch would use him for aggressive Charro style riding when he was originally trained for English. I found him in his stall standing with his nose in the corner refusing to come out. He was so overweight from overfeeding and so angry and aggressive.
I stood in that stall for days just talking to him and caressing him. I could tell he was enjoying the attention and was listening attently be the movement of his ears. I moved him to a new ranch with a trainer who could retrain him to the English style. First though, he had to get rid of the aggression. Anytime I got on him he would buck me or anyone else right off. He had also picked up a lot of bad habits like the ones you described. In a matter of just 2 weeks he is a happy, calm horse. We can now ride him for an hour before he gets frustrated. Though he is still scared to jump.
I simply take him out into the fields to graze and sit with him, talking to him or petting him. I think he thinks I'm part of his herd now since I'm not riding him. He gets very excited when he sees me walk into the ranch. I think for these abandoned horses they need to reestablish a herd. They have such a herd mentality that to be all alone psychologically traumatizes them.
I'm sure that as your TB gets more and more comfortable and relaxed, he'll drop a lot of those bad habits. The bad habits simply replace the anxiety he is feeling since he was all alone without a herd.
Of course, I could be wrong...I am no expert. I simply speak from my experience.