Sure looks like you're going deep enough (IMO you could afford to not go as deeper to add some lbs to your squat).
And about the butt going back, yeah that's pretty obvious too. As you read Ripp said in that thread, think of tightening up and pushing up not back. I also think that sticking your knees out and forward at the top 1/3 of going down, then keeping them out there until you are back to the last 1/3 of coming up will force your butt to go up instead of back.