You’re correct about the first part. The intent was for the devil’s part to be technically correct, but discordant and forgettable.

The call and response was because they were references to other famous tunes. Fire On The Mountain was an old folk tune. House Of The Rising Sun was an old folk tune. Etc… They were meant to be familiar and melodic snippets that people from his area would recognize, to contrast the devil’s forgettable solo.