1) Wouldn't the GM give such an obvious clue on the very first day, as if there were more Mafia members than townspeople?
2) If it weren't me, I would definitely vote for Nick, but the fact that it is me gives me the opportunity to think... And in reality, it's true: The City looks like too obvious a clue (besides, what killer would leave their nickname at the crime scene in the form of a note!??) as a diversion, but the white paper and blood... Seem inconspicuous, but in my opinion, they are the most significant clues. For now, Sten (blood) and Ulrik (note that he has red streaks under his eyes in his signature) are under suspicion.
2) Okay, but how do you connect them to the City?