Here's a book with great ideas on bombproofing: Bombproof Your Horse, Rick Pelicano, Book - Barnes & Noble
I feel your pain, though. I used to have an off track TB. He was out of his mind. He spooked at everything... was constantly leaping sideways into small canyons and then finishing off with a bucking fit. If he didn't do that, he would rear. He was a very dangerous horse. I was young then, and didn't have the sense to do what I needed to fix him, so I let him go. I'm glad I went with a draft horse this time!
You're on the righ track.... do the work on the ground. You may want to get a lead rope with a curb chain if you don't already have one. It's important to spend a lot of time with the horse without desensitizing so you guys can bond... he needs to learn he can trust you. Basic lunging will help, too, so you can establish yourself as the leader. The worst thing you can do is let the horse avoid the things that scare him. Have strange things laying around while he is tied and you are grooming him. Eventually, he will get bored with them. Take a lunge whip and tied a plastic bag on it for de-spooking. If there is a particular area where he throws his head, don't let off..... keep the bag there until he relaxes (cocks a leg, blinks, or mouthes). Good luck!