To begin with 16ga is a little small for any fuel pump IMHO. Something in the 12-14ga range would be much better and I would lean toward the 12ga myself. Your reading of 12.5v with the engine running is WAY too low. The alternator should be pumping out between 13.0-14.6v at idle depending on circumstances, and the voltage at the fuel pump should be within ~.2v of the reading you get at the battery or alternator. I would strongly recommend replacing the ENTIRE wiring for the fuel pump from your voltage source all the way to the tank and also inside the tank and then to ground. Also, make sure you have a good chassis ground as that is just as common of a problem as the positive side of the system. What size is the fuel feed line on the Jeep ? For an application such as yours the feed line should be 3/8" minimum. Most FI applications I see use a 3/8" fuel feed line anyway, but it's worth checking. But, it sounds that the likely source of your problem is the power and ground to the pump. Other than old age and high mileage, wiring issues are the next most common cause of fuel pump failures and also repeat failures such as your experience. HTH,
Phil