I'm actually amazed you managed to get anything by calling USCIS. VAWA privacy protections outright hide most information from the view of the call center employees, so they might see that it started in Vermont, but they generally won't see what happened to it down the line. That's also the reason why the standard operating procedure here has been to just ask a congressman/senator to inquire with USCIS on your behalf. Call center either won't see anything or won't see the whole picture of what's going on. VAWA units are also a black hole that in theory you can write to but they never respond on their own.
1. Not for VAWA. They (as in Vermont or Nebraska) generally will hold I-485 until the I-360 is approved, then pass it to the NBC which will do their own review and can RFE you, then they'll pass it to the local field office which can also RFE you, interview you, or both, and the field office will be the one to issue the ultimate decision on the I-485.
2. Depends. It could be just for medicals. If it's an old filing from back when I-944 was a thing then they could want an I-864W from you (RFE notice will be boilerplate for I-864 and sponsor's taxes, ignore that, fill out an I-864W and send that in instead). If there's any other concerns like arrests they could also ask for that. Basically we can guess, but you won't know until you see the notice.
3. Probably like a week or two. These things go by standard mail, so the closer you are to Lee's Summit, Missouri and the closer you are to a major city the sooner you should get it. If you don't get anything in 2 weeks then you should ask a congressman or senator to nudge them to re-send it or get you an electronic copy.