The bar is twisting/un-even on the last and 3rd rep(4th rep was better), the left side is twisting outwards/back. The GMing isn't too noticeable, but it's definitely there on the last couple reps.
Trying to keep you elbows under the bar(as opposed to behind) and squeezing the fuck out of the bar, pulling into your back should help with this. Having the elbows under helps keep the chest up, which helps keep the back arched and stops you from GMing it as much.
And Frank's right, pull you shorts up or get shorts which finish at/above the knee for squatting!!!
But your form was not that bad(you told us to rip it apart hehe - on that note, I wonder what your last set looked like
post that), and
congrats on a BIG PR!!!