Gatsby and Point of View

So, I just finished reading The Great Gatsby for the third time.  I am preparing to teach 11th grade English next fall and needed to brush up on this classic.  It's a great book, obviously, but it definitely made me think about my own writing too.  I admire this novel for its simplistic, but natural dialogue.  The voice is clear and accurate.  But I've always been curious about the point of view.  As I have mentioned before on this blog, point of view is probably the most important decision a writer can make.  Nick Carraway's point of view in Gatsby is interesting.  For 90% of the book, it works, but I noticed that at the end, it bugged me.  Nick is forced to make assumptions about what Gatsby was doing or saying when he wasn't even there.  It makes me wonder if Fitzgerald all of sudden found himself in a tough spot, trying to relay Gatsby's (spoiler alert) final hours when the first person narrator wasn't even there.  A tricky situation.  

As I write the sequel to The Ridge, it definitely makes me consider my point of view.  What issues am I going to run into later?  As of now it is in