At the beginning, one thing that stood out to me the most was "He needs to SHOW his character, not TELL" yet when I reached the end I saw why you chose this particular format.
Since this chapter hinges on the bang at the end, you may want to get a better hook going at the beginning to really suck the reader in so they actually GET to that awesome bang. (If this is a first draft, or even second, I understand. they always come out like this )

Two small things:
"stubby beard" means "short and stout facial hair"... which is pretty accurate but I think what you were aiming for was "stubbly beard" as in with much stubble.
"He was always sort of engrossed in himself" Wonderful usage of the word engrossed (I'm glad to see this as I work alongside people who don't know what "inflammatory" means...) however the piece is "sort of" too casual. Let me rephrase that... The piece is "rather" too casual. ("rather" will flow a bit better and not sound like a teenager is telling the story)