The biggest thing I notice is the movement of your back. Your shoulders are rounded forward and you hunch over the fence. You're not bending at your hip hardly at all, and your upper body is too upright so when the horse stretches his neck over the fence he pulls your arms and your shoulders.
You need to pull your shoulders back and push your chest out and stay that way. Then bend at the hip. While taking the fence, push your chest down towards the horse's neck but don't forget to keep our shoulder's back and your back straight while you're at it. This will make it easier for you to crest release without the horse pulling your shoulder forward and pulling you out of position. It will also anchor your hips more for a quieter seat. And a quieter seat will help you maintain a quieter leg.
Here's an example of what you need to be striving for: http://www.horsegroomingsupplies.com..._3564711_n.jpg
My trainer always told me to pretend to be showing off your chest and your butt. You want to keep your chest out and your butt out over the fences and not rounding everything in.
It may also help if you try to maintain a good posture when you're not riding. This will help train your shoulders back and your back straight and will condition those muscles so you'll better be able to stay that way while you're riding.
To be honest, your riding is really not that bad. There are a few things for you to work on but they're relatively easy to fix with a bit of determination and practice. Keep working at it and you'll get there!