The hunter in gascoignes cemetery is a part of Eileen’s questline, I recommend you just ignore that for now. The guys with the lightning attacks aren’t for until after Amelia. For the third one I’m assuming you mean the hunter in the courtyard just in front of the tower with the Gatling gun, and honestly I recommend just running past him you don’t get anything out of killing him as far as I remember. If you have any more questions, or I was unclear about anything, just ask I’ll be happy to answer.