I would do a lot of jump the fence from a trot, halt, turn and jump the same fence. WHen he can do that calmly, I would try canter, halt, turn, canter fence, halt. Pretty soon, they realize that they are not going anywhere in a hurry, so no point to rush.
Sounds like he is getting excited and anticipating the fences. Once he can calmly do one fence, then try a line, halt, do the same line...slowly building your way up. Also, instead of spending a whole day jumping, I would just add in a few jumps into your flat work...make it "no big deal".
If he is running away from you down the line, then that is a FLAT WORK issue (IMO), and NOT a "jumping" issue per se. He needs to be more responsive to your rhythm and commands.