Nice post John.
If you need some additional ideas I would buy Bas Ruten's drills CD. I have it and use it when I work the heavy bag. The only problem which I think Yael highlighted is that you will end up hearing Bas in his Dutch accent all day long going 1, 2, 4 three knees. Other than that it is a great workout.
I imagine that the doorway is the best available place for now, I would try to find some other place so that you can work your movement. John points this out but you don't traditionally want to try and move straight back when someone is punching back.
What we think, or what we know, or what we believe, is in the end, of little consequence. The only thing of consequence is what we do. -John Ruskin