Peiker maimed Yashur, so he is not one of the Messengers. Perhaps the Messengers killed Ment, and Yashur is one of the Guests. Some of the Mafia definitely killed, as besides them, the second Man (he visited Rudoy) and the city leader could also kill (but I doubt he would have used his ultimate ability on a random player on the first turn).

I think this is exactly what happened. Execute MyHighness.

Done quickly. For me, "light hair" is more associated with blondes than with gray hair. We still have a block from the first Mafia. They probably wouldn't have used the block + sergeant's ultimate; most likely, the second night's action was a kill. So, Ment is on regeneration. I wouldn't risk executing him, as he is likely to be the Doctor. On the other hand, not going into the Night Night Vision on the first turn would be original :). By the way, we have a clue about the maniac:

During the investigation of the crime scene, a fragment of an old article about the Franco-British meeting in San Remo was found.