The ballast resistor limits current to the coil when running.
You could look up the part number in the '62-73 parts book on the Tom Collins site.
https://oljeep.com/edge_parts_man.html Then search for that number online and see if there are any matches.
Next I would look at what part an online listing like RockAuto shows for the resistor.
Lacking that, we sold a lot of these ballast resistors for a '70s Dodge as a universal application back in the day.
https://www.rockauto.com/en/catalog/dod ... istor,7052
Universal-ish for passenger cars from the era. It'll work. I'd get the RU-11.
Any two wires in parallel will share the current, splitting it in proportion to their resistances. This is current, not voltage. Ohm's law, V=IR. Some current will go through the resistor, some through the hot wire. Five feet of 14 ga wire has a resistance of about 0.013 ohms. Your ballast resistor has a resistance of about 100 times that, so roughly 99% of the current will go through the hot wire.
Your graphing multimeter is making this more difficult than it need be. Any floating wire (open circuit) will have no voltage drop at its end, so the voltage you measure at the coil should be the same with or without the hot wire, as long as the points are open. The condensor is in parallel with the points, and should be an open circuit at DC, when the engine is not running. If it's bad it becomes a resistor to ground at DC and forms a voltage divider with your ballast resistor. Turn the engine so the points are open, turn the key on, and measure the coil voltage. Compare that to the battery voltage.