Try to find good ways to differentiate him from Slendy. What does he look like? How does his behavior differ from Slenderman? The more you can seperate him from Mr. Tall the easier it'll be to play around with him and come up with something really cool and unique. What ways does he use to drive his victims crazy? Is he paranormal or mortal? If he's basically just human, trying to drive people crazy, you might try something along the lines of "Gaslight", i.e. doing subtle things that slowly make the victim feel like they're losing control, and already insane. Maybe he's more phsyically active then Slenderman, in which case he can move around and show up in places he shouldn't be. Like, maybe when the protagonist is talking you see the faintest shadows of him walking around outside.
It's a broad character and there are a lot of things you could do with it, go crazy! Try watching other things outside of the Mythos for ideas, old Hitchcock films for example. As for the channel name, what would make the most sense for the protagonist? Why does he start the channel and what would he have called it? If your character makes the channel for a school project, it doesn't make any sense for it to be called something like "TheStalking" or something, you know?