car won't start until I release the key from the cranking position.

BTW there is an error in the above schematic. Look at where the 2 brown wires come together above the voltage regulator; there should be no wire from that connection to the I terminal of the VR. Otherwise, you would always bypass the low resistance side of the ballast that is in series with the coil + when the key is in RUN.

There is no 'start side' and 'run side' of the dual ballast. The high resistance side feeds a power signal to the ECU (which was done away with later) which I understand is simply a control signal. The low resistance side of the ballast is in series with the coil as in the single ballast system.

In START with the dual ballast, power is fed from IGN2 (on the brown wire from the ignition switch); this puts +12v direct to the coil + (as in the single ballast system) and also BACKFEEDS VIA THE LOW RESISTANCE SIDE OF THE BALLAST, jumpers over to the high resistance side of the ballast to feed the ECU power input (Blue-Yellow wire) and also through the high resistance side of the ballast to the ECU 'control' (Green-Red). The above described backfeed via the low resistance side of the ballast to the high side and on to the ECU is why a blown low side resistance in the dual ballast will cause the symptoms that the OP is experiencing.

When the key is released to RUN, then power is fed from IGN1 (on the blue wire from the ignition switch) to both sides of the ballast resistor at the end where the 2 halves are jumpered together; this feeds power to the coil + via the low resistance side of the ballast, to the ECU main power lead (Blue-Yellow) and via the high resistance side to the ECU Green-Red wire to keep it operating.