Can someone help? I need to drive my dart tomorrow

You can buy a cigarette lighter voltmeter for $15 on Amazon, or $6 for the cheapie LED light one at Harbor Freight. I use in all my new vehicles which have neither ammeter nor voltmeter.

A lot to pick thru. In all your voltage measurements, was the black lead of the multimeter connected to the BAT- post? Voltage measurement is always a difference, so we must know the delta from what to what. When you measured the resistance from the case of the VR to BAT-, your multimeter was on the 200 kohm range and read 0.2, which means 200 ohms. That would be "not good", but is likely inaccurate. Set to the 200 ohm range and repeat, but it should be <1 ohm which is still hard to measure. Better is to measure the voltage drop from there to BAT- and should be <1 V w/ engine running.

You can buy an electronic Vreg that will match your connectors for ~$12. Some are small chrome and others look like yours (see rockauto). The old coil type require tweaky adjustments (see factory manual) and no guarantee a Chinese one will be setup right. They hopefully couldn't mess up an electronic one since the ~14 V setpoint is fixed by a diode. But, I agree with Mattax that your problems are likely in draws from the Pertronix installation or the non-factory wires that go who knows where. People adding electrical stuff to cars that "don't know lectricity" are dangerous, and that describes many mechanics.

Nobody mentioned that you are 1-step ahead by having a 1965. That year and 1963 had bulkhead connectors with large buss-bars that feed the thick ALT and BAT wires thru. Dropping that in 1966 caused endless problems for those owners (i.e. "bulkhead melts" problem). I'm not seeing the "missing insulators" that others suspect on your dash ammeter bolts. I refurbed the dash cluster in my 64 & 65 and looked like yours. But, an ohmmeter would verify they are isolated. The red wire probably overheated not because the ammeter went off-scale (I didn't see that), but rather because it had a little corrosion on the terminals and 50 Amp x 0.5 ohm = 25 W which is a lot of power in a small area and will do that. Sand good until shiny copper on all sides and coat w/ silicone grease. Ditto for all connections, especially those with thick wires. If you give up on your dash ammeter, search for "MAD Bypass" for how to keep the main current in the engine bay.