Some other cards you should consider: Spider Spawning Deranged Assistant Various Skaabs: Screeching Skaab and Armored Skaab specifically.
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Nevermore is a great sideboard - good call. And I'll buy Fiend Hunter as a mind-gamey sideboard card as well.
My concern with Fiend Hunter is that it's far easier to remove than o-ring, and when you're eventually forced to chump, you give them back whatever you took in the first place. Regarding maindeck enchantment removal, it occurred to me that Forced Worship is strictly better than Pacifism in this deck anyway. We aren't attacking, so the "can't block" clause on Pacifism does nothing for us. Forced Worship can be brought back to the hand in response to enchantment removal if necessary, and can be moved to bigger threats later in the game.