I'm going to try and make sense of all the kills now.

Night 1
Laguna - Serah was targeted by Yuffie for a kill, but Laguna was killed. Since it was Night 1 Laguna likely protected himself. The probable scenario is that the Bus Driver swapped Laguna and Serah, Serah got protection while Laguna got the bullet. That also explains why Serah never got a 'report' from Wedge.
I'm going to assume the mafia has two kills, the poison and a night kill. Or there are two mafias. Or mafia and SK. The other deaths don't make sense otherwise. On this night, one killer tried to shoot Nocits while Galuf poisoned Quistis.

Night 2
Quistis - Died of Galuf's poison
Serah - No clue. Standard mafia hit?
Kain - Again no clue.
Quina - Too many unexplained deaths this day for there to not be at least two killers out there.

Night 3
Galuf - This one is the hardest of all to explain. We have a vig (standard vig and daytime vig? seriously?) or something else is afoot. It's not a Paranoid Gun Owner, since we know he targeted Cid (assuming Faris is truthful). Rydia targeted Cid on Night 4 and lived to tell the tale.
How did one scum die this night and no town? So the mafia used their hit to poison Cid. Fine. But this night is sandwiched between nights with 4 and 3 deaths. Doesn't make any sense! Someone must have tried for Noctis again but why would the mafia try the same thing twice?

Night 4
Noctis - My guess here is Mafia Ninja. There are no Mafia Goons remember, so Ninja is a likely role they have.
Yuffie - I think the "second killer" killed Yuffie.
Refia - ?????