Do your arm a favor and spin the engine over with a cordless drill in reverse!
I gather it's a Bosch ignition if you're considering the Foggy fix. Probably a faster solution than continuing down the current path. Or check if Saegenspezi is shipping internationally again and try one of theirs.
That said, if the current coil produces "mucho spark" with your tester, I'm of the opinion that it's a good coil and the problem is somehow associated with the path to the plug and the plug itself is adding just enough resistance to expose a weak point in the path that kills the spark. May want to measure resistance in the lead with and without the plug and see what you have. Shouldn't be any without the plug. A new plug by itself should measure around 50o 0hms.
On the other hand, a good coil should usually jump even a bad spot in a plug lead or mis-aligned plug terminal spring -- usually.
What tester are you using?
