Jumping: Your weight is not in your heels, try moving your stirrup further up you toe even just a half inch. You pinch slightly in your knee, which makes your leg slip back. This may be causing you to throw your body foward ('jumping for your horse'). Your release is quite long, using a regular long release won't catch your horse in the mouth, if that is what you're worried about. I rarely catch a horse in the mouth and I use a short release. It's hard to tell if your stirrups are the correct length because you are up your horses neck a bit. Your eyes are up, and your back posture is flat.
Flat: Besides the fact that your stirrups are too short (I know, its already been said ;p) You, again, should move your stirrup closer to your toe, which will help you put your heels down. In the last picture, even though you're riding in three point, your knee has pinched a bit and your leg has slid back a little and your heel is up.
You look like a good rider, and you and your horse make a really good pair. Your horse is really cute! :)