If I read the original post correctly(a very big if) #6 sticks out. So here I go, with the sender wire off the gauge, you have 30 Ohms? That is a full tank(max Ohms)? Or do I have it backwards? Any way, the sender wire should read something different with fuel in the tank. Like the 19 Ohms in #1, or something very close to that value. Just a bit of wire between the sender and gauge. You can pull the seat back(some screws is all that holds the cushion to the frame), and remove the sender( no smoking please. Turn on the key and move the float. If the gauge moves you have found it to be good. I put a new sender in my 52 3100 and it stayed on empty...thought it was the gauge. Pulled the new sender out just to make a good connection, and the float had ruptured. Instant submarine. I have also seen the sender installed with the float rubbing the inside of the fuel tank. It cannot move and it looks like the gauge is bad. Don't be afraid to pull the sender just to check.
