I'm pretty sure I've figured out what the issue is, though I haven't had the time to try to fix it yet. I'm mostly posting this because I hate finding a post online where somebody has the same issue I have and they never post what the problem or fix was.

Basically, I think the wire coming off the park lamp relay (and feeding PK/LP RH and LH) has a bad connection or something. Those two fuses have no power, but the fuses themselves are good. I took the relay out and tested it and it's good. I used the test light to probe both the high and low amp power coming to the relay and they're both hot. So the relay is good and getting power, but it's not getting to the fuses. With the relay out, jumping from the incoming power to the fuses turns on everything that should be on. Obviously, then, jumping from any fuse getting power to the cold fuses gives them power. Notably, jumping only one will power the other one, meaning the connection between them is still good.

Power should come out of the relay and then split before going to the two fuses. So if power comes to the relay (and the relay is good) but doesn't make it to the fuses, and the fuses are still connected to each other, it seems like the problem pretty much has to be between the relay and where power splits before going to the two fuses. Since nothing looked melted when I looked under the fuse block a week and a half or so ago, I'm going to guess the connection coming off the relay is loose or something. But I won't have time to get under the fuse block and look again until Saturday. In any case, I'm hoping it will be a relatively easy fix.