Okay maybe I'm jumping the gun on asking this but how is it that Bambleby can somehow rip holes into someone else's faerie realm but he can't do the same to get back to his own?

Yes, sure, I can think of multiple reasons why. But if there's not even an attempt to explain this it feels too arbitrary to me. Perhaps some faerie don't care but if this can be done I can definitely see faerie wars being waged and conquering/colonialism being done with the human realm as a cross-universal corridor.