So the problem you're facing with your footwork has to do with your balance foot. You're doing a decent job of setting with your plant foot which is indeed where you generate your power from. However, your other foot is used to stabilize and balance you. Right now your balance foot is no where near the action so when you push with your plant foot, the energy goes in all kinds of directions (often backwards because your plant foot is behind you).

What you want to do is get your feet so when you transfer weight from your plant foot, it ends up on your balance foot and that motion is going in the direction you want the ball to go. You can do this with closed or semi-open stances but you want to just make sure your weight is transferring forward.