You're extending your back with the unweighted squat. Your front squat looks fine. There's no need to go that deep but knock yourself out if it's not causing back or hip issues.
Never mind whether or not it exists. Why would you think a tiny drop in calories from where you were plateaued (ie. no weight change) would suddenly cause a catastrophic change in your metabolism?
It's frustrating reading posters simultaneously say that they can't lose weight at what they think is 1500cal and then suppose what they think is 1300cal is dangerously low. It's okay...