In answer to question 2: the Black Crusades of the fluff are all ones run by Abaddon - you would not use his numbering system for your own Crusades.

In answer to question 1: FFG have previously said that they aren't allowed to change or alter any fluff already covered by Games Workshop, hence why they make their own settings - so they aren't stifled creatively. Therefore, the chances of having in-depth info or campaign details for the Eye of Terror, and getting involved with Abaddon and the like, are slim to none.

With that said, there is nothing stopping you from checking out the Lexicanum and reading up on all of these things and integrating them into your own campaign.

That can be particularly enriching if your players are WH40K fans and they "get" it. Mine aren't, but they're still having fun just without the added "oooooh, cool" factor.