1) I doubt there'll be much if any in the way of in-game content so expect disappointment. Don't expect the KS in game bonuses.
I don't have high hopes, but it's not out of the question. Unless I'm mistaken, I don't believe there was ever a promise that those items would remain exclusive to kickstarter backers, only that they were items kickstarter backers would receive.
If anything, I suspect they won't be included as CE extras simply because that would be of little use for kickstarter backers (who are already going to receive them). It's unfortunate these extras weren't extended to Steam Early Access (which, to me, is just another way of being an early backer). Divinity: Original Sin on Steam is $40, where as the Kickstarter Potion and Zandalor's Trunks of Epic Intelligence only required a pledge of $10 through Kickstarter.
Now I'm going to end up owning a physical Collector's Edition & a Steam digital copy as well, which is paying for the game twice (five times for me, actually, as I purchased Steam copies as gifts for friends).