SQ: Filming from the 45 will give more information. Tray and bear down on your abs a bit harder when you take your breaths to keep your back flat. Lean over more at the start and try to pair this more in sync with your knees bending. Then aim for the bottom depth to be just below parallel - some reps are too deep.
PR: Squeeze your abs and quads tighter before each rep. Make sure you reset your setup before each rep with elbows slightly in front of the bar and tight armpits. Once you lockout the bar for a second, bring it right back down - you are holding it overhead longer than needed.
DL: Filming from the 45 will give more information. Separate all the steps a bit more cleanly. Get your setup, then set your gaze about 10' in front of you. Then without moving your legs/hips, squeeze your back flat slowly by pulling your chest (only) up. As you do this squeeze the slack out of the bar. Then pull.