starting issue

I would still say it's your ignition switch. Classic example of one that is worn out. Your distributor has a "hall effect" sensor in it. It does not have a traditional "pick-up", but it is a sensor that sends an on-off-on signal to the computer. Power is supplied to the TFI module, hall effect sensor, computer, and all other computer-related items by the ignition switch. Sounds like the "run" position of the switch is failing, since it starts just fine, thus eliminating a failed relay of some sort. Since the ignition switch is a cheap part to replace, I would start there.

My 85 ranger did the exact same thing.
It was a manual, so I was able to hold the key in START and release the clutch to disengage the starter motor.
As soon as I would let go it died.

It was the ignition switch on the ranger.