Deep scratches can cause all sorts of trouble. It's possible something gets shorted somewhere in the PCB and in such case theres nothing practical you can do.
Perhaps a good idea would be to check if theres any further damage?
I found sometimes boards have oxidized contacts within the memory slots or even PCI or ISA slots

Doing a quick google, could you remove the BIOS battery for a while? (even though it's probably soldered in...nothing to loose, right?)

I'll keep checking for other problems. The battery attaches with a header and didn't come with the board. I rigged up a 3.6 volt pack for it but it didn't help (in or out). The detachable battery was nice, otherwise it would have ended up like my other 386, with blue trace-eating gunk all over the place.

a20 problem is the keyboard

"In what was arguably a "hack", the A20 gate was originally part of the keyboard controller on the motherboard, which could open/close it depending on what behavior was desired. "

If you trust the BIOS to diagnose the problem correctly.

there may be a setting in the bios for fast a20 gate handler try changing it or try another keyboard

I finally got around to trying this again.. no luck, but I noticed the 8042 is socketed and could, in theory, be replaced (probably not at a very economical price, given the low chance it will fix anything). I have never heard of anybody replacing that chip to fix the problem, but it seems like there might be a chance. It seems to be customized by the vendor so I'd probably have to get the exact one.

Unrelated, I also got an older and much slower 386sx running again, well mostly. Can even get it into Win95 courtesy of an impossibly slow 2mb Aboveboard, but it is, let us say, impractical.

the a20 gate handler is not on the board its on the keyboard
did you try another keyboard ?
that is the fix that worked for me every time

> the a20 gate handler is not on the board its on the keyboard
You are wrong.

The 8042 chips are sometimes interchangable between mainboards, so if you have some to try...

you could be right there, but it is on the keyboard controller and changing keyboards can fix he problem, ive done it myself a few times

Good news. I found a replacement AMI 8042 on ebay (what are the chances), got it tonight and popped it in, and it worked! One Baby Screamer back from the grave.

Haven't gotten it going 100% yet. The jumpers don't match any of the guides that pop on the net - its a series 42, so you'd think its a Mark V Baby Screamer, but it doesn't match the layout. It doesn't match the Baby Screamer LC layout either. But I've got enough to boot, which is a lot better than before.

Thanks everybody for looking at it.