Battery in Trunk wiring completed, now no power at all

The welded splice is after the amp meter, so in a stock setup, if the amp meter is disconnected, so is the battery from the entire wiring harness.

Not sure in your case, though. Not sure why you have power on both sides of the amp gauge. Best suggestion I have is to connect amp gauge wires together with a screw (assuming you don't want to connect the gauge) and see if things work. Betting it will make a difference.