I would also confirm totally isolated that the fuses were OK, not trying to check them while still in the truck.
I think I would connect up to the controller with a GE handset direct to the traction controller, and set ALL the settings to the factory specifications for this truck and motors sizes, if possible. I would also check those numbers that you expect from voltages at the pot. (not saying they are wrong, I haven't confirmed what they should be, but 8ish is usually closer than 10ish in these).