Keep your shins more vertical while you go down. It looks like at the bottom your knees are about 4" in front of your toes, bring it back to about 2" in front. After you reach about halfway down, your knees should no longer be moving forward. With your knees and shins anchored in place, your butt will drop down. Make sure your upper back is kept arched and upright while this all takes place.
Your grip will be easier if you keep your thumbs on top of the bar.
Try looking slightly down while you squat back up.