^^ There are problems with refueling. How much gas can you pump without electricity. How do you collect food, when any room or building could be thoroughly infested. How do you take a crap...
Agreed about the giant dinosaur bug. Given the characters' already precarious emotional states, I have no problem believing that that thing changed everything. People do funny stuff under extreme duress.
And please note that the film ending is more
hopeful for the rest of us humans who appear to survive, unlike the total question mark of the novella.