Horror w Arkham (trzecia edycja): Śmiertelna głębia nocy

Unless instructed otherwise, use all Dead of Night content while playing with the expansion. Shuffle encounters, headlines, allies, items, and spells into their respective decks; keep the new event deck separate from encounter decks (p. 1).

No. Keep the new event deck separate and use it as instructed by the scenario; the rules specifically say not to mix event cards into the encounter decks (p. 1).

Do not look at its back until a game effect instructs you to. Wanted is double-sided, like other condition cards (p. 2).

Yes. Elite X from multiple game effects is cumulative; for example, two instances of Elite 1 give a monster 2 additional Health per investigator (p. 2).

Remove all matching encounter cards from the game, including matching cards in the event deck and event discard. Shuffle the event deck afterward, but do not shuffle the discard pile into it or change the discard pile’s order (p. 2).

When removing one, take a matching token from the cup if possible; otherwise take one that has been drawn but not yet returned. When adding a token, put it directly into the Mythos cup (p. 2).