Not the person you asked but for 1. there is the "primacy of action" bit in the Refereeing advice on page 16.
Essentially "player actions always come first": if they've already done things that would contradict future omens, it's the omens that change (whether that's being adjusted or simply not happening)
Omens are thus kinda like, "here's the timeline of what happens UNLESS the players change things" (whether that means stopping it or just changing the circumstances). So rules-wise it's entirely possible for myths to get resolved before the 6th omen (but still interesting to hear from dannycrieswolf's experience what happened in practice of course!)