from the xp counter in story mode, and other little pick ups, then i can give a guess that story will be co-op, more than likely with only 2 players. Also i noted the gun model on the ak. athough it looks better than fc2's ak, its far from perfect...and dont get me started on that reload animation
but more than likely, they will fix those small problems when the final edition launches.
Doubtful.
I sincerely doubt the game will be co-op. Co-op is a pretty huge thing so you'd think they'd come right out of the gate and say "Look at this, we have co-op." Also, the animations are probably not getting changed. Ubisoft hasn't really been one to be super accurate about their real-world weapons, at least in the Far Cry series.