If I try to play this guy on stage 1 of Breaking of the Fellowship , what happens?

I think you would complete Dunedain's effect as much as possible. You would look at the top 5, pick an enemy, but when you try to put it into play engaged with you, nothing happens and the enemy stays in the deck. You would then have to discard Dunedain hunter and shuffle the encounter deck.

This is my opinion. The hunter instructs you to put the enemy in play engaged. Since you can't do that, the enemy is never put in play. Then the hunter is discarded because no enemy entered play.

Thanks for the quick responses!