Probably just didn't think of his wife as a "friend" even though she probably does fit that best friend description. Semantics, whatever.

I really have no clue if I'd kill my friends or not for my greatest wish. I don't think I know what my greatest wish is. Right now, there's nothing I can think of that would cause me to kill my friends without them knowing it's coming. But in those cases, I'd be killing one or more of them for things that are less than my greatest wish, because I think of wishes several tiers greater than what I'd be killing them for, and none of those involves them dead.