Simple question,

Is the content of the http://www.uesp.net/wiki/Lore:Fourth_Era of the Fourth Era official?

probably not, it would be hard for the Dragonborn to be both master of the college and harbinger of the companions

Pretty much. Canon regarding the player is pretty much determined by the player.

Although the early years of the 4th era are all out of whack. http://www.imperial-library.info/content/fourth-era