1996 Chevrolet Tahoe drivetrain & axles problems

The location of the brake line has caused a hole to rub in the gas tank. ) while driving at high speeds the headlights go off and eventually they come back on after the switch cools off. (3)while driving the tahoe a loud clunking comes from the middle or the rear of vehicle, which sounds as though the rear axle or driveshaft is loose and going to fall off. The dealer is aware of the problem. Dealer not able to correct the problems.

My 3 year old daughter was able to shift the vehicle from park into neutral without the key in the ignition and without depressing the brake causing the vehicle to roll backward into the street. No accident or injuries occurred as my father was able to reach over and hit the brakes.