1. This try should be scored two points. Here is my reasoning, along with NFHS references.

4-41-4 "The try ends when the throw is successful, when it is certain the throw is unsuccessful, when the thrown ball touches the floor or when the ball becomes dead."

These two highlighted parts seem contradictory. Let us put this on hold for a second.

5-2-1 "A successful try, tap or throw ball from the field by a player who is located behind the team's own 19-foot, 9-inch arc counts three points. A ball that touches the floor, a teammate inside the arc, an official, or any other goal from the field counts two points for the team into whose basket the ball is thrown."

This seems to suggest that if the ball bounces on the floor inside the three-point arc and goes in, two points are scored.

I am not sure about past rule interpretations (where I am sure this exact play is fully covered) but here is the rule interpretation for 2012-2013.

4-41-4B "A1's three-point try is short and below ring level when it hits the shoulder of: (a) A2; or (b) B1 and rebounds to the backboard and through the basket. RULING: The three-point try ended when it was obviously short and below the ring. However, since the live ball went through the basket, two points are scored in both (a) and (b).

I know this situation involves hitting a player and not the ball hitting the floor however rule 5-2-1 above treats the ball hitting a player or bouncing off the floor (inside the arc) the same. This leads me to believe that the basket should be scored two points.

Coming back to rule 4-41-4, I would argue that although the thrown ball has touched the floor (which simply ends the three-point try), it is not yet certain that the throw (as a whole) is unsuccessful.

2. The ball is dead when the try ends. According to the reasoning above, the try has not yet ended because it is not yet certain that the throw (as a whole) is unsuccessful.