there was also a blown (looks like it poofed, totally black) 15uf tantalum cap on the board. I'm only guessing it used to be 15uf based on other tantalum caps on the board. Completely turned to carbon, no schematics anywhere online or in the service manual. I just replaced it with 2 electrolytic caps, a 10 and a 5. Might get a proper 15uf tantalum one since I have to make a minimum order anyway.
this was an eBay find claimed "working", I get it and there's lithium ion battery acid turned into this white powder all through the machine... could probably fill a drinking glass with all the acid powder. The way it was stored it ate a hole through the case metal, not the board. Even with this apparently faulty power supply, I still managed to get it to boot from a floppy once. It just needed about 7 minutes once the power turns off before it'll turn back on successfully again... Hoping replacing this cap will fix it.
When the machine is on, the 12v line reads 12v and the 5v line reads 5v.
about measuring ohms on the double cap, it behaves exactly like you said, it's measuring 232 kOhms right now and still slowly climbing.