Okay, but I think you got lucky. On the other hand, since NW doesn't have an international contract of carriage on their website, it might be reasonable to argue for it.
Maybe, but it was the first person I talked to. So I would definatley try again if I got denied.
I couldn't find anything for "international" contract of carriage, either. The only mention of the fee was in the "domestic" for $50.