So this is where you are at. New coil, ECM, Ballast resistor, Ignition switch.
Lets say you did the above and found it all checks out good.
The grounds can and will be a problem. If I remember correctly you addressed the problem. I will post a diagram that shows the grounds that are over looked at times.
The distributor needs a ground if it's point distributor.
View attachment 155869
As said above let's say all the parts you changed are good. It keeps going back the run and start circuit. Bad, connection or ignition ground. There is on other thing that does act erratic. Electronic components 99% of the time work or they don't. Electrical connections and components will act erratic until a complete failure.
The one thing that wasn't addressed is the distributor. The
pickup coil in the distributor will act that way or the connection any connection. Even a ground