Nate, I'm keeping those options as my last resort. Hopefully I won't need to go that far. Fingers definitely crossed!
Chino, that's my plan. I'll try to boot into Windows on the iGPU and revert the GPU Tweak profile to "Gaming." Think that will work?
It should be the latest version of GPU Tweak II, I just updated it in mid-November.
Oh, and I should add that Windows is booting, just with no signal to the monitor. I can enter my PIN to log in and get the windows startup chime and hit Win+X, U, U and shutdown the system.