1st. Pic. It looks like you are in a bit of a chair position, and your leg is swung forward. It could be the position of the camera though.
2nd pic. NEVER look at the jump. Try to keep your upper body taller. Try to get off his neck.
Vidio.Get out of your knee a bit more. It looks like your using it to keep yourself in the saddle. Try to sit on your pockets, it looks like your leaning forward a lttle too much. Good halfseat.