Really enjoyed this, and the sound and birds make me want to reread the Dark Half (Pangborn should have told Henry to get his head checked for tumors back in the day).
More seriously, just want to throw some king knowledge out, especially as to Bills real status. Starting with if telling the truth and this started in 91 it does not explain the rock, Cujo, Dark half, the strangling murders and many other things happened before that, so if true it's not the source of the rocks evil ( if you do want more info on that there is a story in nightmares and dreamscapes that goes back to the corruption, it involves lovecraftian breeding and a Winchester mystery House sort of structure).
And none of that says he didn't come out of a thinnie, they don't always correlate one to one in time and space. It could lead to alternate castle rocks, it could also dump you out in the basement of the Dixie Pig. Besides he probably came from todash space if that's really his point of origin.
Also have a nitpick. If the kid got off the bus in the 'lot, it was night, last I checked in the King universe the 'lot is officially a deserted town and people that go in at night are never seen again. I don't see the bus stopping either it's known. So in effect to shove in an Easter egg they actually contradicted the whole point of it.
Also I actually liked the crazy innkeepers, felt like what I wanted from this, the town as the point and all the fucked up shit the people do, I think a great case study of how a castle rock story should go is Needful Things, the town and the people are the story, all the Devil did was Bring it to the surface. The fire was already burning all his shop did was grab gasoline and use it as an accelerant on the already dangerous situation.