Since both the fuel gauge and the oil pressure gauge are erratic, a bad ground comes to mind as the cause. Clean the grounding point and reattach the wires.
As for your generator, it is designed not to run when your fuel tank is below 1/4 to keep you from being stranded in the middle of no-where, as you indicated. However, I'm under the impression that this feature has to do with the placement of the fuel pickup from the tank, not the fuel gauge, but that could just be the way my coach was set up.
