You look a little tense, almost like you're trying too hard! I know in America they like you to curve your back and stick your bum out, but over here our jumping position is a lot less stylised!
I would advise you to relax and go with the horse over the jump
To me it looks as if you are holding your back too rigid, in the cantering picture as well. Relax your shoulders, worry less about your position and more about your balance! Also ideally would like to see a bit more bend in your knees - for jumps of that height you barely need your bum out the saddle, perhaps your stirrups could go up a hole
You have a lovely horse, and you're a nice rider
Just worry less about how your position looks, it will all come naturally
Are you planning on taking him show jumping? I think he'd enjoy it!