Your lower leg is slipping back and, as you noticed, your weight isn't in your heels. A lot of two-point at walk, trot, and canter should help with that. Your release is exaggerated but if you started jumping last November, since you are pretty new to it I think over-releasing is better than catching your horse in the mouth, something you seem to be aware of, which is great! You may want to begin to shorten your release slightly, however, so you don't have to fix that habit farther on down the road. On the flat (unless those pictures were taken while jumping) you may want to lengthen your stirrups a couple holes- you always want to ride with longer stirrups on the flat and then shorten them for jumping. Your upper body is a bit too far forward even for hunt seat on the flat, so focus on stretching up through your core and chest. Really focus as well on wrapping your legs around the horse- you seem to be pinching with your knees a bit. You are always looking up, so great job on that- I'm still trying to break that habit :). Your horse is absolutely adorable by the way- he looks so sweet!