I’m going to very slightly disagree with Roger here (doesn’t happen often). Not about the mechanics but about how to get there. You all know about my recommendations re: reverse progressions. I suggest that the hip into the fence drill is fine to get the feeling of what causes the front hip to get going. Where I have another idea is the towel drill. I’m not going to get into a big discussion about the drill. I’m just going to say that I don’t think throwing the ball is a bad thing. You’re doing well with that and I think you can handle it. My suggestion is a different “drill” that Roger has recommended to some others. It’s the one where you stand at the rubber, as in pitching from the stretch, but you cross your front foot over and behind the posting foot. Fire your hip sideways and then free up that foot and pitch. Finishing with the throw, rather than stopping or using a towel, puts what you’re doing into specific context, which I believe is a very good thing.
You mentioned not feeling balanced and in control. That’s the point, you’re not “balanced”. Your centre of gravity is not over the supporting foot. If you didn’t get your front foot going, you’d fall. This is an element of how momentum is built up toward the plate. You’ll adjust with practice and get used to it. Watch Tim Lincecum. He’s an extreme example but he does prove that you can do it.
As for the back foot, I kind of agree with Roger. The core firing is the real point here and focussing there is effective but I suggest that sometimes the knee can “hang” out toward 3rd, inhibiting hip rotation. My recommendation is to think about rotating the entire back leg, along with the core. Spin the enitire thing. The foot will turn over and the toe will drag as a result.