Epic thread.
Even though you got the demon to work better did you do any road testing with the holley?

Myself, I would do everything I could to prove it was or was not a particular system. Same results with a different carb would make me look at a different system. After you've checked fuel pressure as mentioned of course.

How sure are you the ignition is isn't failing when put to the task?

You may have mentioned either but it's hard to keep up with all the spins this has taken.
You'll get it eventually, just comes down to how much time and $$$ it takes.

Edit: Might be worth it to pull the heads just to make sure they aren't full of carbon build up.
Or one of those nifty borescope to peak around in there.