Im really glad that you read this, too! And I'm even more glad that you enjoyed it -- in spite of Peter and Dung being not particularly likeable -- and that you commented. Bless you for that!
Peter's motivations for the betrayal are a bit of a blank in canon and I wanted to look obliquely at that. As you say, Dung does nothing but allow Peter the space to examine his position in his friendship group. That's a start, though. I like to think of this as the start of the devastation to come.