Very insightful comments trag, thank you. I played a bit with the CE pins before, attempting to make a direct connection to ground which didn't help. I think I'll test the voltage between ground and the CE pins of the onboard ROM chips with and without the jumper installed. If it doesn't produce good clear logic levels, I shall trace around and see why.

An amazing advancement was made on this old IIci today! I plugged it in, with the IIfx ROM and it lit right up, and BOOTED successfully into A/UX, showing 20MB or RAM. I think possibly there was still some moisture somewhere that hadn't quite dried yet from when I washed the board, and this is why it works now. There is hope for this old baby! It definitely needs new caps. It does the "always on" thing, where if you shut down it will reboot after a second or two of being off. So we'll see. I will also inspect more carefully for damaged traces from cap goo.