I think you have two problems assuming you did get a good ground at the instrument cluster. The turn signal light is a classic case of one of your parking light bulbs not being fully grounded. These bulbs contain two elements with the common between them grounded. If there is an inadequate ground, there is a sneak path of current between the parking light and the turn signal light. So when you energize the parking light, the current doesn't go to ground but rather travels up the turn signal wire. Happens all the time. I would pull each light bulb one at a time and use an alligator clip to go to a known ground. The other issue sounds like a bad ground at the fuel sensor.

BTW, where are you in Colorado, I am out here on business for the next few weeks. If not too far, I could potentially lend a hand.