Hi CJ,
Squat: Looks like knee cave is the culprit for your inability to hit that last little bit of depth (you're very close, by the way). I can see your left foot is pronating at the bottom, cluing me in to knee cave. So shove 'em out hard to the sides. That should help you get a stretch reflex out of the bottom.
I'd also advice lowering the bar in the rack just a little bit. You've only got a little bit of clearance and if it gets heavy and you get sloppy and tired, it could be a recipe for missing one of the uprights. Lower it just a bit to ease re-racking, provided the next rung down isn't too low - then you'd have a choice to make.
Belt? If you want to. Try it and see if it teaches you to do the valsalva maneuver more effectively.
DL: Your pants are baggy - I can't tell if you're touching the shins to the bar after you do the grip step. Also, you've pointed your toes out a little (good), so make sure your knees go out as well. Lastly, keep the bar against your body for the descent. It's okay to let it down fast, but it has to happen against the legs.