I think your half seat and 2 point on the flat could use some work. Like ErikaLynn said, your seat doesn't seem very secure. Your heels should be down more, and you look like you are slouching in some spots (example 0:25).
Your hands also need a lot of work. When riding on the flat, you should not have your hands so far up the horse's neck. It's like you are never coming back from your jumping release. They are also very bouncy and you don't seem to have good contact with the horse's mouth. You should have a short enough rein that you shouldn't be able to see the reins bouncing up and down.
Also, when turning a corner, your hand should never come out and away from your body like you are "leading" the horse (example 2:03). You should only need to pull back and toward your body... never out.
Overall, I think you look pretty tense the entire time. In general I think your poition over the jumps looks ok, but I agree that you need to work on strengthening your seat before you work on any more jumping. I would suggest doing some cantering without stirrups.
No hour of life is wasted that is spent in the saddle. - Winston Churchill