Having followed your trials and tribulations on Discord, I can only say: Bravo, ol' chap! Well done!
The sort of tinkering I wish I had the space for.
Tell me more about your plans for an already quite insane PM9600?
The NewerTech is a cool addon, but could be one source of issues.
Did you try booting with the G3 removed?
There was a 110MHz model released late 1994.