Fuel gauge. Again.

There were a few very technical responses in another recent fuel gauge thread.
A fault between limiter and circuit board was the root cause of that limiter putting out high voltage and both gauges going to full. Owner bent the male spades on the limiter a little and poked it back in. It's cured, for a while atleast.
So now that you know your problem isn't at the sender, you'll need to check that gauge, its connections to the circuit board. The mounting nuts are its connections and have been found loose before. I wont go into what the inside of that gauge might look like and why the needle cant travel as it should until we know the fault isn't on the outside of the gauge.
What puzzles me in your comments, full tank of fuel ( 10 ohms through sender ) gets half full reading, then wired to ground ( 0 ohms resistance ) gets just over 1/4 tank, or did you mean 3/4 tank ? Zero resistance should have taken the needle to its fixed stop, a bit beyond the 'F' . Only thing that I can think of is voltage supplied to the limiter. Like maybe the engine running charging voltage is 12+. Then only switch on is a bit less than the full 12 volts. Less in is less out. Hope this helps.