The engine starts on the .5 ohms when the ignition switch is on "start" and when you turn it loose it goes to run position and runs on the 1.5 ohm side. I bet the ballast is either backwards or the connection from the .5 to the 1.5 side is broken.
"Backwards." The original factory connections are polarized to prevent this. If the polarizing key is broken off or the connections aren't original, that could be, but will not prevent the car from running........poorly, probably
So far as the "starts" and "runs" this is not correct. One side of the ballast supplies the coil........exactly as it always has, with points
The other section of the ballast supplies the ECU. This "need" was eliminated in later ECU boxes
The start circuit is somewhat convoluted. The brown from the ignition switch feeds the coil directly. The ECU during start gets power by means of a feedback circuit from the coil + back through the ballast, only during crank.