He was spinning pretty bad just before the chute opened. They had said that the shoot would automatically deploy during a spin if he went over a certain amount of G-force. I don't know if that's what happened or not, but that would be my guess.
No, Felix managed to regain control of the spin himself, despite it being a very difficult task when encased in a pressure suit. But his visor was misting up to the point of being unable to see his instruments - in particular his altimeter. He deployed the chute because he could no longer be sure of how close he was to the target deployment height.