Couple things that I'd do next is make a jumper and go from the tank sender (70ohm or 126ohm) to the BK wire. See if you get a reading. 0 ohms appears to be full, so more than 0 is less then full. I would guess that 70 ohms should read something. Go to radio shack and get a couple resisters, say 10, 25 and 50ohms or something like that and put them between the ground and the BK wire. It should read something less than full.

Back to bypassing the switch, if the fuel levels show up, try and jump the power. If the pumps work then it's the switch.

David