@Jessey I was going to say the same, 2.5 weeks off is nothing even for a green horse.
@MIT15 what you describe sounds very much to me like a horse that potentially has ulcers and is also rather sensitive generally. Being very sensitive along his sides is a classic example - I used to have one prone to ulcers and believe me I learned to keep my legs very still and never ever ever used them beyond a certain point - as is being very one sided and indeed going into a blind melt down if pushed on that rein. He was also jumpy about stuff behind him and it was always wise to make sure nothing was unannounced. I bought this horse from his breeder and he stayed with me all his life, there was no abuse it was just who he was.
With regards to his response to a fast movement towards his neck or quarters when ridden, had you considered these are the areas a jockey/work rider would use a whip to encourage a surge forward? You may very well have a unwanted but trained response here and realistically under normal riding there is no need for fast rider movements in these areas.
My current Welsh cob can be very jumpy around people he doesn't know and again I know his whole background and there is no abuse in it. He's sensitive and, to put it politely, reactive and simply does not respond well to fast movement, loud people, the wrong body language and people he doesn't know getting in his personal space. I've had people say he's been knocked around and it really isn't the case, more knowledgeable people see him for what he is, act accordingly and get the trusting sweetheart he really is
Re not getting answers from the training yard, I live in a racing area and I can tell you that anyone pestering a trainer for "answers" would get very short shrift, particularly if you imply abuse. These aren't pet horses, and in many cases once they're gone they're gone.
My advice is talk to your vet again in detail and discuss the possibility of ulcers. Check the damage to the jaw isn't causing a problem either in his mouth or his neck. Get some help from people who have a lot of experience in horses coming out of training, they are not the same as taking on a youngster. Work with what you have and stop looking for someone else to blame. It may be that you have the wrong horse for you and it would be better for everyone to move him on to a home experienced with racers and with full disclosure of what you have problems with.