RE: Deadlift vs Squat poundage...muscle imbalance?
I don't think you have a muscle imbalance. You just have a relatively stronger back than legs, for now. If you keep training, eventually your squat will probably exceed your deadlift.
Another aspect is form. To squat truly big weights you need to adopt a powerlifters squatting form - wide stance and bar low on your back. The wider stance uses more hip and glut muscles, which can support more weight than the quads, and lessens the strain on the knees.