Sending hugs your way, Chewy
I am glad you and W finally talked. I do hope he sincerely apologised for his part and for hurting you. I know you probably care for H, but I think it is best to just keep things on a platonic level. She is a proven liar and manipulator. Those are qualities I would not want in a girlfriend or in a friend. H probably magnified K's asshole like tendencies for her own benefit. If things were that bad, why is she still there? Ten times to one, this is not the first time she has cheated on him, and if I were K, I would divorce her. Hurting you got her what she wanted, and she seems like she was not going to let anyone get in the way.
I would strongly suggest closing your marriage, rebuilding the trust, and working on your relationship with your husband. I would not advise adding another person to the shambles right now. I know you are hurting. You found out about an affair, fear that H only used you in some very messed up plot, and everything else.
I feel bad for you and K. Pawns in a game. Forgive yourself, if you feel that you were wrong in anything you did. Be it continuing to help her lie to her husband or whatever else. You will grow from this situation, and well, life slows down for no one. I wish you the best of luck, and I hope you guys can work it out and move forward.