I haven't saw the movie since it came out, but I remember the roomie being fake since the start. He was out with his 'friend' but nobody else saw him, just like at the army base. He was asking the guys who big brother was, and they sorta just shrugged it off.
I remember the mailbox being some empty dump, but wasn't that when he got 'involved' with the big brother guy? So, wasn't that a different operation than the code breaking?
I would watch it again to find all this out, and to give you my opinion with a fresh outlook, but it was so depressing. I don't think I could watch it again!