1)Salinger died recently in 2010.

2)I agree that this wasn't written in the style of Holden, but then again anybody in this entire fan fiction section who thinks they write like Holden is clearly mistaken.

3)Lastly, if you'd like to sound like Holden, then more important than the slang is to have something to say and to say it. Salinger is full of insight yet most people who attempt to imitate are so nearsighted they can't see past the author's narration.

Sorry I seem so brusque, I just am not in the mood for writing, but I thought these tips would help. I haven't read your fan fiction much at all, but these things were quite apparent when I skimmed.

Keep Writing.

This wasn't really written in the way that Holden would speak. Sure, you said the word "phony" quite a lot but that doesn't make it sound like him.