Well, this episode sure threw a monkey wrench in my theory. With Chibiki coming out to explain everything, I don't know where to start.
We now know that Misaki (the mom of Mei) is central to the mystery, there's now a Mikami-sensei, who was a teacher in 1996, who may be important, and the date of 1996, 2 years ago, where it is hinted that there has been some memory-alteration going on.
Everything in the episode is just plain weird. I didn't understand most of it and they all seemed to me like false flags, red herrings to throw people off the right track.
At least now with the very very very very very cute "dance" sequence we can confirm that in Umineko style,
the narrator's (Sakakibara) perspective is unreliable, not everything can be taken as literal truth.
Oh and before I forgot