A few things on your backhand. First, understand that a 2hb is basically a left handed forehand. Your left hand is dominant and swings just like your right handed forehand. Your right hand is passive. Second, instead of letting your racquet flop down below your hands on the backswing (you don't do that on your forehand, do you?), you should hold the racquet head straight up (close to your head), with the face facing the side fence on the backswing and then let it drop below the ball on the forward swing, and snap it up and across the ball with a dominant left hand. Third, you need more upper body rotation, back and forth. On fh and bh, a grounstroke is mostly upper body rotation, not independent arm swing. You are trying to swing too much with your arms and not enough with upper body rotation.
Hope that helps.
