Couple of quick things I noticed. One, keep you upper body more upright, bend more with your knees and less with your waist. Two, keep yourself centered on the board. If you look in the video you can see that you have less bend in your leading leg than your trailing leg, hence you are leaning uphill while riding. Keep yourself centered with both knees bent equally, it may feel like you are leaning downhill, but you will initiate turns easier and have more control when you hit choppy terrain.
I at times notice myself still leaning on my back leg on steeper terrain and have to correct myself. If I am washing out alot on high speed turns it is usually because I am leaning uphill. By leaning uphill you are taking weight off your downhill contact point, making especially heelside turns harder to control.
There are members on here that would know better than I though. I'm better at correcting myself than correcting others.