Well, thats some pretty nice skiing to start with. It looks best in the sections where you've got some open space to link turns a little more consistently.
It is a little tough to get a solid diagnosis if you can't watch more than a couple turns in a row, so I'd definitely suggest next time you're out videoing, find a good pitch where you can get a lot of turns in view of the camera, and have your friend stand at the bottom and film you from a fixed point - makes for a much better video to watch from an instruction standpoint.
The one thing that really stands out to me is the lack of ankle motion. If your ankle isn't moving along with your other joints (hip/waist and knee), you can be doing everything right, but still end up with your weight back, and that can throw everything else off very easily.
If you look at this crude diagram I've just made, you can see that in the first case, the shoulders and knees aren't lined up overtop of the toes, and hence the skier's weight is to the back. In the second picture, he has the exact same angles at his knees and waist as in the first pic, but there's more bend in the ankle, and that re-aligns the rest of his body in a nicely centered position.
I would recommend getting your boots looked at by a good boot fitter. From the video it looks like they're probably too big, or at leats poorly fitted, which is a surefire way to make it very difficult for you to make the proper movements, especially in terms of flexing your ankle.
After that, there are plenty of good exercises for getting ankle motion into your skiing. An easy one is to stand nice and tall and open your ankle up at the start of your turn, then as the turn goes, flex down, trying to keep your toes, knees and shoulders all aligned like in the second diagram. It's hard to tell if you're getting it right, so a short lesson would probably help a lot, and the instructor can give you some extra drills to work on.