The type of saddle does not make a real difference, except in one’s mind. Have you tried just letting him stop and take a good look at whatever he thinks is scary? That helps mine somewhat. Another thing that helped (although it sounds crazy) was taking Valerian myself, so that I am less edgy, and therefore less likely to affect my horses. It is available in the vitamin section of almost everywhere, and won’t make you groggy or anything else that could create a dangerous situation. I grew up with TBs – on and off the track, and generally they were less likely to spook at things because they experienced so much that the average horse would find terrifying. As for bolting, one thing that can work well is to turn him in a direction he does not wish to go. He’ll stop. He should also consider that a cue to slow down and stop is for you to stand up in the stirrups and lean a bit back – watch a video of a race and you will see what I mean. It might also help you if you can get someone to longe him with you on him, preferably in the arena, so there isn’t really anywhere for him to go. Your other boarders do not sound like very helpful people, and help with someone who knows what s/he is going is what you need. Is this just a boarding facility, or is there a trainer/instructor available?
It is never the horse's fault