a) How do you handle the interaction Joey the Rat & Yibb? In a 4 investigator game, in order to remove a doomer from Yibb's doom track, do you need 9 (4*2+1) or 10 [(4+1)*2] successes?
b) Do headlines influence investigators in OWs? Some of the MH Headlines are quite nasty (Strange sleep disorder baffles doctors! for instance). Since Environments rarely affect OWs, I don't think a Headline can affect investigators in OWs, but a feedback from the community is really welcome
a) X=number of players per doom token. Yibb makes that 2X; Joey adds one more. 2X+1.
b) Ah, the old "how do the cops/lawyers find me in the Abyss" question. We are all creative and/or clever enough to come up with a story to explain any number of wacky discrepancies between reality and Arkham Horror: "Maybe Cthulhu hates whiskey too!" So it comes down to, did the card say "In Arkham" or not? If it did not, then the effects affect your investigator regardless of his or her earthbound status.
And for a "creative" answer: your Investigator still needs to sleep, even on Yuggoth or in another dimension. If the Dreamlands really exist, couldn't you get to it from anywhere you happened to close your eyes?