Lets look at the mechanics here :)
Firstly, as already stated, you are jumping ahead, common practice. But lets look at everything to break things down.
First, look at your feet. See how you are reaching for your toes? Notice how your heels aren't sunk?
One of the most important factor to jumping, is being solidified in your tack and to do that, you must allow your heels to be your anchors. Your bodies weight must naturally flow from your head into your seat, and from your seat down into your heels. The moment you grip or pinch or tighten up in your body/body parts, you've blocked that flow from naturally occuring, which leaves that weight from dispursing into your heels.
Once you've figured out how to allow your bodies weight to flow down into your heels, where they can anchor you, move onto what George Morris stresses - you are not ontop of your horse, you are wrapped around your horse. So, heels absorbing bodies weight, find your balance over your feet, learn where that is, and then wrap your lower leg around your horses girth. Opening your knees and allowing your lower leg to solidify around your horse.
Work on a lot of two point, heels doing their job, leg wrapped around horses girth, balanced over your feet. Activate your core.
You mentioned that your lower leg flings out behind you when you go over bigger fences - if you work on this, I am pretty sure you'll become quite solid. Remember, the moment you grip or pinch, you block that flow from occuring, which in turn results in the lower leg flinging out behind you, and your upper body pitching forward.
If you can, start reading George Morris's critique columns in the Practicle Horseman Magazine, he also has books and DVD's out as well.
Also - when you are approaching a fence, don't focus on it. Meaning, don't ride the fence, ride your horse. It's your job to get your horse to the fence, rhythmic, strait, balanced - it's your horses job to do the rest.
You can't jump that fence for him, it's your job to stay balanced over his center of gravity, and out of his way so he can do his job. The moment you start to focus on the fence, and forget about your horse under you, you stop doing your job. Let the fence come to you, not you to it. Ride your horse, not the fence.
Another thing that I learnt from an Upper Level Eventer, is to think of your body angles like the angles of an acordian fold. You know when you close an acordian and the material folds close as the acordian closes? Imagine your knee angle doing the same, and your hip angle doing the same.
So instead of opening them when going over a fence, close them. Close your knee angle, and push your seat back towards the cantle.
Your release - it looks as though you were grabbing onto your horses breast plate for that Trak fence. Not a biggie, I'd do it too if I had to.
The Banana fence, again, you lost your lower leg.
Work on your two point, allowing that weight to naturally flow - it's just about muscle memory and once you've trained your lower leg muscles as to where they need to be, it'll be easy peasy from there :)