I suspect 2 problems:
1. triggering points in the bottom of the distributor (first suspicion when
only half the injectors work)
2. worn out ignition switch (electrical part only) because when you are
cranking ignition is fed through a contact on the starter that bypasses
the ignition ballast resistor to give you a hotter spark. Once you turn the
key to "run" (as opposed to "start") you are no longer feeding current to
the ignition system through the starter bypass. So it could fire while
cranking but be intermittent while running if your ignition switch is headed
south.

I doubt that your ECU is going bad unless it has water or corrosion in it
but sometimes the connectors get an invisible film of nonconductive corrosion
product ("tarnish") that makes connections bad. Removing and replugging a
time or two usually helps.

BTW I have a 73 145, awaiting an engine rebuild (40 miles/quart of oil)
AKA "The Yellow Peril", and I used to have a 73 164 (AKA "Righteous")
that gave out in San Simón, Arizona on a trip east. Both had the D-jet
and the Yellow Peril displays very similar symptoms to what you mention.
I probably will have to replace the switch in it. (When I get the engine
together.)
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma