I don't think Jan killed Kono - I think she just got caught in a lie and was embarrassed. It seems safe to assume she didn't stab herself, so there's still someone out there commiting these crimes. We know Tim had access to apartments at one time, so maybe its possible he had broken into Jan's apartment and stolen the cleaner thing.
I feel like Bunny is too old to be physically assaulting people. I suppose she could have shot Tim, but she would have to be careful approaching a young guy like that.
I feel safe saying these people didn't do it: Mabel, Old Dimas, Young Dimas, Jan, B