I don't know much about foals and how their genetics play into the height, so I won't bother commenting about that.
His trot seems nice and free. It is fast, but it could very well be just because he's young, unbalanced, not used to where to put his feet, and doesn't know he should trot slower. He seems to stretch nice and well at the trot. He's not just plodding along, not tracking up. He's looking great! And he sure is a cutie. C: You seem to be doing wonderful with him.
It's where I learned about working hard
And having a little was just enough