I don't have the drawing skills required.
That's like super major spoil alert and saying what happens here would anger a lot of people who would see it, but to give a half answer, nothing "ultimately" happens to Sodachi because Koyomi reverses it all in Zoku. The fact remains that he did wear her underwear, but well - I won't spoil all of that fun. Zoku doesn't really -center- on Sodachi though, although her very existence in it is a mild slap to the face for Koyomi.
in Sodachi Fiasco, Sodachi gets kicked around in a trash can, probably in Osaka, and loses all of her (fake) friends she kind of didn't make, but is a cooler person for it. She continues to have an bit of a twisted obsession with Koyomi.
I like her, but I reserve full judgement until I can read my stack of fan novels I have about her that I've been meaning to get to.
Yotsugi is everything and everything is Yotsugi.
THE WORLD.
I dunno, they're spooky.
Nope. Though I do sometimes describe it in less geeky terms on purpose. In Japan I generally tend to talk less about it though. There are far fewer people to talk to around here though in general.
Zui/Sui and Taiho got pretty shafted.
The one that Veto played at though I didn't end up staying until he played because I got sick. "orz
Sour Gummies.
My teeth are going to fall out and my bank account is going to be empty at this rate.