Stop creating sparks at the battery. It may explode. I've seen it happen a dozen times and it ain't pretty. Acid on paint, all over engine compartment, not to mention the risk to your eyebones.
Check it with an ammeter to see if you have a high draw. Sounds like you may have a bad alternator (yeah, I know you had it tested). Full field the alternator by jumping at the VR connector, I don't remember which wires, but Google should know. If voltage goes up, reg is bad. If not, something else. Maybe alt, maybe wiring.
Ford used fusible links in the '70s. They're usually near the starter relay. The insulation burns when they go, look closely, sometimes it's hard to see.
