I think it would be quite embarrassing, if Fain plays yet an even more Gollum-esque role in the end. RJ was certainly a bit more creative.. But a lot of people believe in it.

IMO, "The future teeters on the edge of a blade" is just another metaphor for the currently completely uncertain and dangerous situation for mankind, because the Shadow might yet win at TG ( of course we know that the Shadow won't win). A similar expression is e.g. "all that is, all that was, and all that will be shall balance on the point of a sword" or the image of a pair of scales from other Prophecies. "The great battle done, but the world not done with battle" probably refers to the battle at Tar Valon or another big battle before Tarmon Gai'don actually starts.