Seems like a door general location has been estimated.
But even with how difficult the door will be to find, will sealing it be any less difficult?
Kind of reminds me of a part in the Graphic Novels "Fable" when Pinocchio had to convince his father that the White Queens plan was doomed to failure. Sure, technology wise, the mundane world of CNH might be a few behind that one, but could the Fey world have held out if the queen really did dedicate herself to war with them?
Obviously, there's a difference from the mortals they dealt with in the past and the ones in those times or ones in current times.
It'd be interesting to see how a steel or iron bullet would work with fae. Probably poorly. ;-]