Hi,
Running from the start, may be you overlooked something obvious ( it is often the case, by experience !)

IF it fires back in in the carb, it means you have spark.......non ?

Voltage is normal,
Ecu is ok...
wires are fine

Is the cap worn or damaged ? if not...
The advance plate moving freely? (not stuck)

Lessen the advance just a notch on the dist to start..(not supposed to turn backwords when turning off)

Did you check the level in the carb ?
Clogged primary jets ?
Have you tried putting gas in the carb and start it? if it does you'll know where to look..

Dan