Yes, I remember Emeth. 
(I didn’t remember his name, since it’s been close to half a century since I’ve read the Narnia series, but I have thought about him in the interim.) The distinction in the article between universalism and inclusivism is good, and agree that neither are heresy, as opposed to pluralism and universalism which are.
We can trust our good Father, that he just and fair. Just as there are degrees of reward, I suspect that there are degrees of punishment. (And speaking of Lewis, noting The Great Divorce here is appropriate.)
I also remember reading (probably longer ago than I read The Chronicles) an account of an aboriginal tribesman in Africa who knew that the animism of his fellows was wrong. So he set out on his own, leaving the tribe, seeking. And he was found of Christ because in his travels he ‘happened’ upon some Christian missionaries laboring in or among another tribe or tribes. I wish I knew the citation for the story, because I don’t think it was apocryphal.