Dense movie watcher needs clarification

Rating: Null/10 (24 May 2004)

SPOILER!!! So I'm watching "A Beautiful Mind" tonight, and I'm utterly confused about when the reality ended and the delusions started. When he was first summoned by the government to decode the numbers on the big screen, when Ed Harris was standing above him, like "big brother", was that real? If NONE of this was real, I am truly dismayed that they wasted so much movie time leading us on and letting us thing it was all real. I kept waiting for his illness to appear, only to find out that it had already happened!
And what's the deal with everyone at Princeton giving him a pen towards the end of the movie? What is the significance of that?