As for the Children of the Forest being led by the three-eyed crow, I'm not going to disagree. Somehow I think the three-eyed crow is more of a priest-type than a leader, though.
Question: is there anything in the books that points towards the seasons becoming longer? I mean, were they ever the normal length? I'm not sure about that part of your theory, but I do think that the CoF and the Others are instrumental in balancing out the world's dark and light sides. I've often wondered if they aren't simply showing the two faces of one god (Rh'lorr).