I think that the idea of Marcho saving the day is a good one. Fordogrim is really just putting on a brave face: he's wise enough to know that without help soon, they're all in a lot of trouble!
What's more, I think if it were "that crack-brain" Marcho who saves them, it would really stick in Fordo's craw. . .
BTW -- I don't think we need to discount that third wolf so quickly; she's down for the moment (and presumably in a lot of pain) but she's still very much in the fight!! (Fordogrim does tend to get ahead of himself from time to time. . .
)