Thanks for the tips
...PSU is healthy (loaded and unloaded) and the backup battery is a solid 3V. I'm getting good voltage and signal readings on the PCB test points, although it is hard to determine whether or not they are all correct without the full service manual
The backup battery and everything around it appears to have been changed at some point, so that area was of particular concern for me, but all the resistors and caps around there seem to be doing their jobs.
I DID notice a small bit of white corrosion around several pins on one of the SRAM ICs, possibly from whatever got spilled in it, especially if it was something corrosive like soda. Could a fried SRAM chip be giving me these types of symptoms?