Bryan,
I have installed half a dozen of these now and enjoy them more each time. I use the generic GM harness. I agree about the power windows, however I have yet to have one cause a failure. They are hot all the time on the painless. It actually turns out okay especially in my 69 Vette when I want to drop the top, etc, I don't have to put the key in to lower the window...and it is really good the couple of times the car got caught in the rain in a parking lot without me or the keys and my wife or others were able to pop the top up and run the windows up without the key. Running to a dedicated 10 gauge wire through a key on relay however would be better, I agree.
On the back up lights, the harness has one side hot with key on and the other goes to the back up lights. I can see how that would be easy to mix up.
I think the feed and the run are both light green. I have to double check for sure.
It's all fun.