Ahh, I couldn't resist. Got a late night urge to fix this thing.

This trace is also bad

Some older pictures of some of my vintage computers:

Continuing: this alone didn't help. Still broken.

Because the RAM slots were so badly affected, I ended up tracing them out.
Everything checks out, including the 74F244 buffers to the RAM. /CAS however is perpetually high after a short burst of activity during start up, so there is never even any access to the RAM after that.

Going by the error codes, it does have problems during the RAM autodetection phase. It hangs after step 13.

I went back to the 74F00 NAND gate I replaced and found another broken trace. Fixing this also didn't help at all.

A Vogons post

I'll probably have to take off the uppermost SIMM socket. I can see corroded traces underneath. And although I have traced it all out and everything checks out, there could be still sufficient unneutralized base under there that provides enough of a current path to throw off the chipset. Will try rinsing it again with vinegar and alcohol. If that doesn't help, I'll have to take off the socket. But that's going to be really ugly, judging from my experience with the NAND gate.

I washed it, dried it thoroughly, no dice. I also mapped out the Data lines to the chipset now, because these are the only traces that could still be affected. Everything checks out.