You can learn 2 Witchcraft Skills in Gwen's hut (you need 1 Talent Point for Witchcraft). A third one if you later side with her when she turns Athia human.Yes, I'm going to try again and finish this mission first, thanks.
By the way, any advice on which talent to maximize? How do I unlock more combat skills?
Corven teach you Combat Skills if you ask him AFTER you rescue Arianna.
You need 7 Hunting Points for the 1° Skill. I don't remember how much you need for the 2°, but with 10 Hunting Points you are able to learn the 3° Skill.