I commend your bravery and I see a softer side to Kevin I am kinda shocked by your compassion towards this animal in a way. I have learned in my experiences with horses thus far that MOST of them can be "fixed" as you say BUT I have also learned that some can't...some just have a crossed wire or something and it just comes down to risk versus gain. I wouldn't want to be legally responsible for this animal thus I wouldn't ask anyone else to do it. BUT if you are willing to take on that sort of liability just to save an animals life it speaks volumes about your character. You are a sweetheart...awwwweeee. I wonder though if they are capable of just being "off in the head" like people can be. Like the Charles Manson's & Jeffrey Dahmers of the human species...where maybe not even from their own doing...something in the brain just doesn't click or is misfiring and no amount of "therapy" can rectify the damage. I have only my own knowledge pool to dip from. I have worked with a lot of horses and only seen a couple that were just to far gone to "save"...that TWH is one. Just something ain't right with her. The best way I can describe it is she "pretends" to be trustworthy and then snap and you are in trouble. Like I said I wouldn't want to own the responsibility of an animal like that...I would put it down...but more power to anyone who trys to "save" it...just let me know where its at so I can stay the hell away from it ;)
It may take a thousand trips past him with a broom or bucket before he starts to realize that it's not going to hurt him but he will realize it.
As for being brave enough to try and fix the horse. Bravery has nothing to do with it. I'd make sure that the danger was very minimal. I never said the OP should walk into a stall with a broom in her hand and the horse loose. I'd tie him up good and stout and walk well out of reach of him. I'd make sure everyone around thought he could kill them with a glance so that they would not only stay well away from him but wouldn't be inclined to handle him for any reason.
If after handling the horse I thought he couldn't get over it and would continue to be a danger then I'd put a bullet in him without a bit of remorse but nothing in the OP or in subsuquent posts leads me to belive that this problem can't be cure safely, easily and probably a lot faster than everybody thinks.