Personally I would like to see your toes facing a little more forward, your arm could be a little more in line with his mouth (straight line from his mouth to your elbow), maybe a little more contact with the bit. You may be a little too far forward. It's hard to tell from just one picture especially with writting across it.
He looks scopy and calm over the jump. Maybe better if he took off a stride sooner.
It looks like you got into the base of the jump quite close.
The reason for that is probably your eyes. The approach to the jump was probably a little fast and unbalanced, and instead of sitting back and relaxing down into the tack and counting your strides you leaned forward, pulled and did the deer in headlights look right at the jump. So your horse ran up to it, lept over it and all I can say is thank goodness you have wieght in your heels!
What you really have to practice is distances distances distances. Put poles on the ground and count 3-2-1 to them until you have it perfect, then move to smaller jumps and focus on just keeping the jump in your pereferal vision, having soft eyes that are up and ahead of you. Keep your weight on the back half of the horse to balance him and keep you elbows soft. If he speeds up too much then sink your weight down and stall your seat instead of pulling. If his running becomes a problem then try bitting up to a pelham with two reins so you have added control with the leverage. But use the curb rein sparingly so he doesn't learn to lean on it. Once you have mastered this at a 60-70cm jump then you'll be back up to the 1.20m ++ quickly! You have a lovely horse and some good stick em in your seat and legs.
With your toes, possibly because you have too much foot in your stirrup can contribute to this prolem. Really make sure you have the ball of your foot on the stirrup pad. Also I think you are jumping ahead. Stuff your butt back more towards your horses tail. That will make your whole position more balances, and prettier. Your relase is fine, it's just that you are tipped foward making your realse look a little non existance. I would say you could give more realease though if you tighten up those reins, which would be a good idea.