I disagree. He's told early on that Abner is dead, but he's still VERY motivated to find the Ark. And his father has to talk him into letting go of the Grail rather than risk death. No such motivation exists for the skulls.
What would you power a refrigerator with in a fallout shelter, when power is utterly knocked out for an indefinite period? It makes no sense at all to think people would live on frozen TV dinners or last night's lasagna, as opposed to, say, canned goods (which need no power to preserve).
I thought the "nuke the fridge scene" was extremely unrealistic (in the first place, there was no reason to line a fridge with lead in an A bomb test, other than to set up the "escape"), but my problems with the film go far beyond that. Fundamentally, it's a dull, uninteresting story. Indy isn't...