This discussion may contain spoilers!
So you may hate me on saying this but I think the murdere is Mister Toad. Why do I think this you may ask? Well now open your ears and listen.
I think Toad killed Faith because he saw her as responsible for destroying his car. She is a worthless hooker in Toad's eyes and she was the one who started arguing with Woddy. This is the weakest link in my theory and i can't find anything else.
The second thing is when you investegate Toad's house you find scratchmarks in the windowframe. As far as I know toad's doesn't have nails or claws to make these marks. Toad says:" I tried to get out the window but he pulled me back in." That doen't make much sense.
I think he killed Snow because she was speaking to her son who had seen Toad kill Faith. He got the impression that she was on to something and had to get rid of her.
It may also be because of Bigby's relations to these ladys. I don't know. What do you think?.