If you haven't already, and have the factory resistance values for the coil, run it 'til it gets hot and quits, then meter it asap.
It may still be the VR, I _think_. The 2800 gets the voltage to make spark from the battery when cranking, but when the switch is released, it has to self-generate the spark. So the VR has be functioning for it to keep running. I didn't bother to check mine for spark before replacing the VR, but doubt it had any.
You really should take J-D's suggestion and ask the mod to move this to the tech forum.
Jim, "The nicest thing about the future is that it always starts tomorrow."