What is the mood in "The Devil and Tom Walker"?
The mood--that attitude that an author evokes from his readers--in "The Devil and Tom Walker" is humorous and didactic. Irving uses the story to satirize cold marital relationships and superstitious, greedy humans. His satirical tone adds humor to the story, especially his description of Tom and his wife's attitudes toward one another. The author also intends for readers to learn a lesson from his story; so the mood is rather didactic.
In response to #1 I think it is important to notice how the mood changes in the story - it does not remain constant, and certainly when Tom first meets with the Devil, Irving creates a mysterious, ominous and brooding tone suitable to the evil personage that Tom is going to meet with. Certainly, overall there is a delightfully humorous tone as Tom gets his just deserts, but that should not blind us to the message of this tale.
Irving has the distinct talent of conveying a strong message in a light-hearted manner. While the mood is ominous with the appearance of the devil, the humor of the termagent wife with whom Tom will not make a deal with the devil not because he will lose his soul, but because he does not want to share anything with her puts a light-hearted spin on this somber mood.
The tone of a story is the author's attitude toward the subject, and the mood is the emotional landscape. The tone of the story changes the mood. So at the times when the story is satirical, you have a sarcastic and humorous mood. At the times when the story is melodramatic, you feel suspense.
No, Tom never becomes a slave trader. The devil offers this to Tom as an option; however, Tom says that he will not stoop so low as to trade slaves. He becomes a usurer (money lender) instead.