If you have access to an arena, and preferably one with at least 2-4 riders (maybe something you can arrange?) bring him out there with a halter, with you just on the ground. It sounds a bit like he is traffic shy. The bucking comes from his lack of knowing what else to do.
Have the riders just be riding about, occasionally venturing closer to you. If your guys acts at all like he wants to just jumpf or joy at all of the excitement, give him a job. Shake the rope at him to back him up, send his hindquarters out and away from you, have a flag and wave it every time his attention goes elsewhere but you..etc..
Just keep re-directing his attention back on you. You have to vary it up, so that you remain interesting enough that he pays attention. If you feel he is not dangerous, have the riders pass by you from the front and behind, and try not to allow him to pay attention.
By teaching him to pay attention to you when the going gets uneasy you'll build a better partnership with trust and understanding.
When you ride him, and you feel that claustrophobic episode coming on, turn him in tight circles until he refocuses his attention back onto you again. And any time he IS paying attention to you, grande reward. Make him feel safe when he's with you.
The ear pinning game, gotta love it..hehe...not.
There's a few things that have worked for me in the past..One gelding I had seemed to have a similar situation and every time he pinned his ears I'd pull a small bit of his mane, then let go when he stopped pinning his ears.
That, or just simply give him a job. Every time he isn't paying attention to you, tell him something to do. Serpentines maybe, or just bending his neck from right to left. And again, I cannot stress this enough, when he's with you, love on him like you never thought possible. :)
It's basically the same concept of the theory that you make what he wants to do uncomfortable or unpleasant, and what you want like a slice of heaven.
Don't treat him like you do your other horses. Just because your other horses tolerate certain things, doesnt mean he will. Treat him as his own individual. Stay safe. :)
Keep us posted