Looks like you're setting up a bit far away from the bar. Your shins have to go quite a ways to meet the bar, and you drop your hips a lot to get them there. Make sure you keep your hips high as you grab the bar and set your back. You're right that you need to squeeze your chest up a lot harder. Point your nipples at the wall in front of you and your butt hole at the wall behind you. Your eye gaze is too close to you. Pick a spot on the floor ~10-15' away.
Shorts are awesome. Remind me of my girlfriend's outfit from her dance show a couple of weeks ago