See, I kinda think that one of the reasons he never got caught was because he didn't LOOK like a vicious murderer. He probably didn't wander the streets wielding a knife dripping in blood with a sadistic leer on his villainously mustachioed face. To paraphrase Wednesday Addams: he's a serial killer. He looks just like everyone else. Or all those people they interview after they catch a serial killer: He seemed like such a nice man.
Personally, I find the idea that Jack the Ripper was hiding behind the facade of a decent person far creepier than if he was wearing an outfit that screams "I just slaughtered three prostitutes!" ... but that's me. We're all entitled to our own interpretations, right? Since I hate painting gore and guts, this was the way I chose to go.
So, for me the challenge will be creating a character who is outwardly normal, but with hints of his true personality lurking in the details. As I add those in, maybe he'll feel more like Jack the Ripper to you. Maybe he won't. But then, maybe that's what I'm going for.