My suggestions are:
(1) Get him to keep his head upright through release.
(2) Get him to stabilize his glove out front. He really swings the glove around and lets it finish behind him. Once he extends it out front at foot plant, he should leave it there and bring the chest to it. The elbow will tuck down and the glove will turn over but the arm needs to be firming up to provide a stable base for the throwing arm.
(3) He needs to lengthen his stride because his head and shoulders are getting out front too soon. This causes him to throw with too much arm and not enough body. It also causes him to fall forward after release. To do this, get him to get his hips moving sooner and faster toward home plate while NOT sacrificing his knee lift height. This will take lots of practice to get comfortable with.