I do want to say, OP, that I think you are giving far too much power to this past "bad experience". From what you have said the horse mistakenly had a saddle put on it, but was not mounted/ridden. I can't imagine someone making such a mistake more than once, so this would have been one time that the horse had a saddle placed on it and then, presumably, removed. That is not something I would allow to color my approach to this horse's training AT ALL moving forward. I am really struggling to understand what would have been so traumatizing about that scenario for a horse as to excuse any of the issues you are currently dealing with. It turly sounds like more of an issue of a horse with NO foundation, not a horse with a bad experience as a foundation.