In NGK world, you are 100% correct. They are the only ones I know of that use higher numbers for colder heat range plugs.
Champion, Denso, Autolite to name a few, all use higher numbers for hotter heat range plugs....
AK...
I'm pretty sure you don't need to explain to me what glazing of a plug is, how it's caused...but maybe you should read up on heat range plugs from NGK..since you did mention a 9 series as apposed to the hotter 8 that comes stock.
Other things to check once you rule out electrical problems are drain all the gas, remove the fuel valve from the tank and clean the fuel screens. You'd be amazed over the years how much crap gets plugged in them.
The last time I had a bike that rev'd out clean and good in neutral (no load) then fell on it's face when put in gear had a nasty air leak at the base gasket and a dip inbetween the cylinders leaking coolant. (Aftermarket, mono-block cylinder)
Without going over your whole post again, here's what you need to do for TORS Elimination.
Clip the wires at the throttle, unplug both ends from the tops of the carb caps, unplug and remove the "brain" under the gas tank, ignition side of the bike, and unplug the parking brake (which...sounds like is already done and I missed that part)
Next thing you'll need to do is remove the gas tank and plastics and trace your harnesses down for a burnt or broken wire....shorting things out. Clean connections to the coil, run an extra ground wire from the engine to the frame/coil mount...
Then you're gonna get into the weird stuff, like a broken, frayed or rubbed wire behind the flywheel/stator...
Have you replaced the spark plug ends that go over the cap. Factory ones are KNOWN to go bad. 4 or 5 dollar NGK caps fix that as well.