Silman's challenge: Light-Squares And Black's Magical a-Pawn

In http://www.chess.com/article/view/winning-the-light-squares-with-blacks-a-pawn, Silman suggests we analyse his game before looking at this notes! So here goes...

Here's my personal 15 minute analysis. Given a blitz rating of around 1400 that might be the quality of my analysis. Also, I've probably been bad in spotting moves I don't like, rather than always finding a better move.