So if the official site is not canon I guess I'll stick to Memory Alpha for my canon reference needs (that is unless someone knows any major problems with their info)
The official site has never been "canon". It's outsourced as a license just like the novels, comics, RPGs and toys. Material written for the official site gets approved by the same CBS Consumer Products process, AFAIK.
is contributed to, edited and info deleted by fans. It's as reliable as Wikipedia, Memory Beta and IMDb. Great, useful resources but... let the reader beware.
gives the year that Spock joined Pike's crew and his rank.
We do know that Spock served with Pike for 13 years (IIRC), so any date that has been pinned down is conjectural, and probably tallies with the one guessed at by the Okudas in the "ST Chronology".
Back story on Arex would be from the two-page biography sold by Lincoln Enterprises in the 70s and 80s.