Typically the voltage at the + side of coil is 1/2 the IGN1 (high side of ballast) voltage, when the negative terminal is pulled low. That is because the ballast resistor is often nearly equal to the coil primary resistance. Because the transistor in the Mopar control box has a saturation voltage of about 2V, the (+) side may run higher. Some say 7V to 9V is typical with engine running. When the engine runs the (-) is going up and down at a rate of 4 times the RPM, so the voltage varies some with RPM.
The IGN1 voltage is going to be slightly above 12V with car off and close to 14V running and charging. You may read 6V off, 7V running.
I would check why your voltage drops to 11.5V, running with some loads on. To me that may be your problem. What is your idle speed?