When you said you ran a new ground wire from the sending unit to the gauge pin and by passed all the Dakota grounds, which wire from the sending unit did you connect to, and did you only connect that wire from the sending unit to the gauge, or did you also connect it to a ground like the frame or something? Did you disconnect the original wire to that pin?

The trucks positive voltage comes from the gauge pin and goes to the sending unit, and then from the sending unit to the ground. When you connect the wire from the gauge directly to the ground, you are telling the gauge the tank is full, so that is why it goes to full. you are bypassing the sending unit. That action should have no effect on the ignition system.

I fail to see how you lost ignition unless you grounded the wrong pin, and blew a fuse. If you connected to the correct pin the most you should have lost would have been the gauge/instrument panel fuse.