Coil failures are few and far between, but it's more likely that you might have a coil with the wrong resistance in the primary winding. Try measuring the resistance of the primary with both wires disconnected. A coil that will flow approximately 5 amps with 9.5 volts applied to it will have somewhere near 1.9-2 Ohms of resistance. 5 amps is the maximum a set of points will handle reliably without burning.
Back to this saga. Engine has been run successfully several times since this thread began, but the weird voltage has been bugging me so I tried a new balance resistor last night and checked voltages just for experimentation purposes.
Old ballast resistor:
12.5 volts at battery terminals
11.7 volts at resistor input (I swear I used to have full battery voltage here, but I guess I didn’t document it)
5-ish volts at resistor output
New ballast resistor:
12.5 at battery
11.7 at resistor resistor input
3.5-ish volts at resistor output
So...if 9 volts to the coil input is considered about right...the new resistor took me the wrong direction.
Jerry mentioned it’s possible I have a coil with improper resistance. I did measure the primary last night and it was 1.3 ohms. What else would I need to do to test the coil? Or just should I just try new one and test the same spots for voltage?
Edit: I did forget to disconnect wires before checking the coil primary voltage.