I am really not understanding your logic on why the WK isn't infected
From what it looks like, he feels that being infected with Nemesis would somehow undo Maggie's Death Curse. Like maybe being infected with an Outsider would make him not just protected externally by Outside magic, but also internally.
I wholly disagree with that, if it is indeed the case.
It's really a toss up, but it hardly matters since we know he was in cahoots with Outsiders somehow. One thing is fairly certain to me though, if the WK was infected, so is Lara (assuming doing the WCV thing to her pop would infect her), and thus Thomas might also be infected.
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Really, we have few solid facts as to what the infection even is, how it spreads, if there is an "incubation" period -there are a lot of questions. Is there some kind of over-mind to it? Kind of a Borg thing?
I think how it manifests varies from person to person. Cat Sith seemed like he was a different being, note how he moved as if not fully accustomed to his body; Compare that to Maeve who seemed much herself, and preoccupied with her own emotional stuff right to the end, rather than achieving Nemesis' goal. Maybe the difference has to do with their metaphysical mass, who knows?