1972 Ford Mustang Parasitic Leak????
 

Tested for amperage across all fuses (fuses installed -- used exposed metal at top of fuse) and got nothing when the car was off and the door pins taped closed. Fuse metal to ground of course results in overload and short on two fuses, presumably because they are involved with ignition or the ciggarette lighter (irrelevant since no amps across the fuse, though).

Any other ideas? I jumpered the negative batt terminal and tested amperage and also got nothing. And yet this car has gone through two fully charged batteries? Any other ideas? Really just two bad batteries? Alternator tested good and car can sustain itself without the battery in place (alternator also brand new). Lol, I know, risky move. I'm at a loss. Any ideas guys? What else could I test?

I'm a little confused on how you tested for amperage drain. What you need to do is remove the fuse then connect the amp meter across the fuse plug in terminals.
The positive lead goes to the slot that is hot with the fuse out and the negative lead goes to the other side of the fuse slot. That way all current must go thru the meter.
If you disconnect the negative battery terminal and place the positive meter lead to the cable and the negative meter lead to the battery negative post , you should get the key off current drain which should be below 50 milliamps or 0.05 amps.

Yeah, I looked up some more articles online and realized I had tested the entire thing wrong. So....I tested between the positive post and cable (riskier than the negatives, I know), and got a reading of 0.000 mA, so there's basically no drain on the system at all, and yet the battery still goes dead. And even after an hour of driving, it still won't charge enough to start it in the morning.

One person suggested that it might be a voltage regulator problem, but the voltage running reads 13.8V, almost exactly what it should (however, the lights do flicker). I don't suspect an alternator though, since the car doesn't die after a jump.

Not knowing exactly what test eq you have, here's something you can try.
Connect the voltmeter leads to the battery , with the engine running, and then turn on the blower motor hi speed , hi beam and wipers. See what the charging system is capable of maintaining voltage wise. With that kind of load and the engine at approx 2000 RPM it should be able to maintain at least 12 volts. If not , get another alternator.
If it does maintain the 12 volts, get a new battery.

Tried it, but it was all normal. I decided to take the voltage reg. in to have it tested and it failed. I have a feeling that it was overcharging and "shocking" the batteries, because after a few days they would actually gain some of their charge back again. Weird, right? At any rate, replaced the regulator and if they go out again, it will have to be the alternator or battery, because I've checked for a drain 5 separate times and there is nothing. :) Thanks hanky! I appreciate the input!