In the diagram posted by
@rsporsche, the black and red wire gets energized by the starter solenoid. It goes directly to the coil thereby bypassing the ballast resistor. When the car is cranking this provides a higher voltage to the coil than what would be obtained by energizing the coil through the ballast resistor (27 in the diagram above). So the ballast resistor bypass does not need to actually go to the ballast resistor, it essentially goes around it from a circuit perspective.
then ballast resistor, you should see 12 volts on post 16 of the coil when the ignition switch is on.
In the diagram above you can see that the other end of the coil primary is post 1. That goes to the distributor points (or in your case one end of the Pertronix unit). I am not totally sure where wire 33 goes (it is also connected to post 1), but it appears that it goes to the test connector 37, and then off somewhere else. If I had to guess, that would be to the tachometer.
I am curious that you say the ballast resistor was getting red hot. There is no reason that should happen unless the coil primary is shorted to ground. Normally the coil primary has enough resistance that it drops 12 volts when the ignition is on and the points are closed (with ballast resistor this would be reduced somewhat by the ballast resistor, so maybe 9-10 volts).
As a test, you might disconnect the wires from the #1 post on the coil, and measure the resistance to ground. This should vary from around zero to very high (10K-1M ohm) depending on whether the points are open or closed. Rotate the engine by about 60 degrees and you should wee this resistance change between zero and some high value. If the resistance is stuck at zero ohms (or near zero) then either something downstream is shorted, or the Pertronix unit is shorted. You can sort this out by separating the Pertronix wire from wire 33. If 33 is shorted, then something is shorted downstream. If these check out, then measure the resistance between terminal 1 on the coil and ground. That should have very high resistance. You can also disconnect the wires from post 16 and measure the resistance between post 16 and ground.If pin 1 is not connected, then the resistance between 16 and ground should be infinite. If it is shorted, then the coil is bad (which would explain the red hot ballast resistor...).
Per my tutorial above on Kettering ignition, in normal operation (not cranking, but with the ignition on) the hot side of the coil should be about 10-12 volts, and the other side should be either zero or 10-12 volts, depending on the rotation angle of the engine/distributor. The coil doesn't care where that voltage comes from as long as it stays on while the engine its running.