Fuel sending units read WRONG time after time!

have you tried to run a new wire from the sending unit to the gauge, just tie wrap it for now, nothing perfect, just to see if the wire to the gause is not damaged somewhere, just a thought, I tried it on mine, I think my problem was bad grounding to the dash or something to do with the dash, going thru 2 or 3 sending units, grounding the tank, and everything you did, sounds to me that the tank end is good, also if you take the sending unit out again, try hokking it up the the wire and going up and down with it looking at the travel