I couldn't see the "before" photo at all. The others don't give a very good view, but my first impression was of the "odd" hind end. His hip angle is very flat. It shouldn't be that flat (see how his tail comes out so high on his butt?). The way he moves might indicate that he has some issues int he sacroiliac joint. When he trots and canters, he hardly moved his back or neck at all. It looked like he was holding it in a defensive way, though he displayed no signs of pain. That would also tie in with your saying he trips in front.
I might have him looked at by a good equine chiropractor.
I like his big head, and his attitude , as shown in the video, is really classy.