As far as I remember you need to go to both witches and inicially accept their offer. At that point you can resign and decide to manage to "fight" Nameless alone or accept her mind-control amulet and meditations to protect from him controlling your body. THEN you will be able to progress those quests further. I know it's not intuitive and this text under quest is missleading, but I THINK this will resolve the issue and you will be able to continue the story.