So for the wiring, you have the colors and functions right. The path is as I said in my other reply. Maybe an electrical engineer can enlighten me here, but when you have a light assy with one power wire and two grounds, mounted in a papier mache panel, I don't see how you can control it three different ways.
1 being cargo light switch that is independent of whether the doors or tailgate are open
2 being either rear door or tailgate
3 being the switch on the light assy itself.