Working on transitions really helps. After the jump, go to the walk, and then halt. It is easier for the horse to collect at a walk, and he won't fall on your hands if you just halt. This will hopefully help him get the right idea
heels down, sit up, maybe even hold the outside rain lift the inside, make sure you have the lead and look ahead.
heels down, sit slightly (really slightly) back and get your horse's attention, a quick squeeze on the outside rein can be enough.
Sit down lightly and balance make sure to maintain leg and if needed try a half haly
"Ice cream scoop" take your feet and act like your "scooping" ice cream. This will give the power and confidence to do it again
Keep your reins of the same length, as it was before the jump hence