No, there would be no residual effects from the black coven.
As for helping to control empathic abilities, please read my response to Nicholl from Woodbridge, VA for suggestions.
Now, I wouldn't be me if I didn't address the whole black coven, white coven, fear thing. I don't know who "he" is, but he sounds like a jackass to me. Forget his name; as a matter of fact... forget he exists.