sounds like you're doing everything right ..
the unknown quantity is what the idiots did to the bike .. yanking on wires or sticking scrwedrivers where they dont belong.. who knows..
i'd resign myself to a very thorough examination of every bit of wiring related to the ignition and it's components .. The trouble may be a simple thing, like that sparkplug wire was twisted and is broken .. Swap suspected parts with known good parts where practical..
i sure don't envy you or what you're going through, but at least you'll eventually come away with much more knowledge about that bike and bikes in general.