Personally, I don't see anger in your nerd. His mouth, by the shape, looks like a smile more than a frown. I was gonna suggest giving him some eyebrows, but it looks like you wouldn't want to distract from the glasses. Maybe you could angle the glasses like you would eyebrows. The AA you use is a bit wonky in parts, like the chin line on his face has a couple places where the AA seems to be backwards.