100 minutes would seem like a "walk-on" for the major attractions on 12/31. More like 3-hour waits for the Mountains and such.
As for phase closings, expect Magic Kingdom to go to phase 4 before noon--given the crowds this Fall and this week, wouldn't shock me to see it by 11 a.m. My guess is DHS will go to at least phase 3, probably phase 4 after MK fills up, but again, just an educated guess. EPCOT has not closed in over a decade, I don't expect it to this year.