Looks like you got some good depth. Hard to tell where the bar is on your back, though. If you get a chance, try to take a video of you outside of the rack next time with more or less the same camera angle each time.
Also, about the lower right back irritation thing, let me know if you find out more about what happened. When I first getting started with weight training the same thing happened to me. I'm fine now when doing squats and deadlifts, but I still have weird twinges of pain in that area if I sit at a weird angle or twist around in a certain way. I actually went to see a doctor about it when it first happened, because the pain didn't go away after a couple of days, and she said it was probably just a pulled muscle and sent me on my way.