Carey's really the writer with the best hang on the character I feel; so yeah, I really love Legacy for that.

Charles, rightfully so, isn't totally sure of Erik which must make things a lot worse for them.
That part I'm not sure I get why. In chronological order, from the fall of Genosha, they have a pretty good relationship up to when Fraction wrote Magneto's arrival on Utopia when Charles' totally bitchy for no reason - which I fanwanked as agreed-upon posturing to manipulate Cyclop into agreeing XD
The thing in the recent series, is well... in the latest issue they reveal why Erik was there with them; and that makes Charles' defiance making a lot of sense for this specifically. Though I like your interpretation! Must have been a factor too :D