OK...what do the different levels do? How do I put a widget (say Power Control) on my home screen but set it so it stays visible regardless of the different buttons (springboards?) I tap?
That's a more complicated question. I'll upload my theme in a day or two with some screenshots, but it's a beast to even try to edit.
"Simple" answer to your question: Create a blank springboard. Select "no" for minimizeable and "on by default". Put it on layer 1. Add a system widget and size it for the Power Control widget. Put it on layer 1 or 2. Have that springboard control that widget. First time you run, the springboard will probably be off but when you touch the screen it will turn it on permanently and you will be set.
If, subsequently, you don't want to see that on other layers/screens above it, you have to 'blot it out" with a colored springboard or, if that color is too ugly for you, a picture object on a layer above it.