I thought the way that "Solution to Saturday's Puzzle" was written was what made it funny. The situation he is in and the way his thoughts are presented makes the text funny. I think a majority of the jokes come from the crossword puzzle when he is filling in words about Becky, himself, or the situation he is in. For example, when he wrote in "I am not an asshole" in the fifteen-letter space, that was a joke. These jokes though aren't funny if you only read the punchline, you need to understand the situation as a whole and thats what make the individual jokes funny. There are many funny parts in the piece but the next joke that I thought was really funny was the end, when he describes the word that Becky called him as they were getting off the plane, shithead.
My joke is: Why did the turkey cross the road?
To prove he wasn't chicken.