I don’t know lots about horses and I am by no means a good rider but in my limited experience TBs are very very quick to react, sometimes explosively so as you have found. You need to keep yourself safe and if you were so scared by what happen that it’s keeping you awake you need some help from someone, let’s hope his old owner can show you how good he is again but in the mean time I would be walking him out and about, keep it short and sweet and make sure you are wearing your hat, gloves and boots and lead him in his bridle with a lunge line attached in case he has a moment, stay calm, you know he can be good, you know the area, so set off with purpose and take charge if he wobbles a bit, baby steps and remember all of this is new to him, owner, yard, companions, it’s all going to unsettle him, it unsettles most horses for a wee while.
Good luck and let us know how you get on.
Good luck and let us know how you get on.