If you want it to work out, try bombproofing him. Expose him to everything you can think of, on the ground (not on his back) and this will create a trust bond and make you the brave boss. I adore Tara- now- but about ten years ago I called the vet to have her euthanized because I thought she was insane. It is a long story but it involved me tying an empty bottle with some pebbles to the saddle and her going ballistic and trying to destroy the roundpen. She wound up kicking my now ex-husbands knee in an attempt to remove the saddle from under her stomach (after two hours of running full blast around the round pen it had slipped) and ripping up her legs when we finally caught her.
I was ticked at her but then of course realized it is truly never the horses fault. They are what they are and we try to make them into what we want. If you apply pressure to a horse you MUST be able to release that pressure and I could not. It was totally my fault that happened.
In the course of several months of daily bandage changing we bonded, looked at scarey things together and now I am proud to say I can do absolutely anything with her. I sometimes carry a bowsaw and cut down branches over her head, I can drag things, pony off her, swim with her, love her to pieces.
I have Arabs that are way more tolerant than her but not as serious about the job at hand.
Lisa