I'm thinking it's Simones father that can see Molly. I'm not sure how, since he's dead and all, but he was also able to see and interact with Peter.
Was that Richard Roundtree? I think that was a dream projection, and that he's a good Freddy Kreuger.
There's no reason for us to believe that Old Man Deveaux is worse than Sylar, which Molly says the person who creeps her out is. So it's not him.
I kind of got the impression that the guy who creeps out Molly was sort of a Randall Flagg type, some uber-powerful baddie...Devereaux didn't seem to be that way. We'll find out, I reckon.