I generally discourage relying on voltage measurements at the coil because they will vary depending on conditions.
For example, Engine off, key in run.
Power supply voltage will be roughly 12 if the battery is in good shape.
Current at coil will be much under. How much so depends on the connections and the alterator field draw.
Also with the ECU ignition, its like the points are closed all the time when key is in run, engine off. So current flows thorugh the resistor full time, making it hotter (and higher resistance) than when running.
When driving, power is supplied at roughly 14 Volts, current flows through the resistor on/off. So running there is a higher voltage supplied to the system plus cooler resistor - and more so at higher speeds.
Some things to check.
Engine off. Resistor should be .5 to .6 ohms
Engine running. Voltage supplied to resistor compared to overall system voltage should nearly the same. Alternator output voltage should be around 14 V, and the voltage at the resistor should be within a 1/2 volt of that.
Its best to do these measurements when the battery fully charged. The ammeter will show whether its recharged or not. It should be finished recharging within a few minutes of starting. If not, charge the battery on a charger and try again.