Your back isn't too bad here. IF it looks like this on lighter reps, you've got a problem. Your hips aren't too bad, but as the set progresses, the bar is getting a little bit further away from you which is impacting your pull. Work on pulling back as you pull up and that will help.
Regarding your PS comment, don't get too full of yourself. There are plenty of coaches on here that may pull less than you but who really know their stuff.