sounds like you're having a hard time with your squat groove because you're trying to change it. if you are a natural back squatter (low bar, low back angle) then squat that way. getting below parallel and adding weight to the bar are the main things. unless you're a powerlifter, back squats are an assist excercise, albeit an assist. excercise for life in general but still, it's hard to fault a form that let's you move heavy loads and hit depth.
also, you're doing lot's of single I see, that helps some people find a perfect groove, sets of 5, 8 and even 10 seem to do it for me..
I did a month of density stuff
about a year ago now that really honed my particular groove, I still need to think about every rep but the basics are automatic.