You've verified a good ground & I was thinking maybe a person could add a resistor in series to up the resistance to reduce voltge to shift the needle back to dead on E when the float is at the bottom of it's travel BUT w it's showing a diff reading each time I'd eyeball the windings & see what's changing/shorting as something is or there is a poor connection somewhere that is changing the ohms but you are physically moving the float/arm between tests so I'd zero in on the windings & check that the arm that slides on the windings has enough tension down on the windings or anything else that dont look kosher.