1. I would say that it made more sense just to take Tommy out. Why get rid of another good earner in Jimmy? Though Jimmy was heavily involved, Tommy had the long standing beef with
Batts and caused that situation. Tommy being whacked should have served as a warning to Jimmy that he musn't screw up again or he would be whacked too(like doing something dumb and getting involved in Henry's drug deals). Also, Tommy being a pure Italian was going to be looking to get made eventually and could have later ended up
as a capo with real responsibility. Better to take the crazy guy out now while he is unimportant and before he has too many friends in high places. Jimmy could never be made and have that kind of influence, but he was in his own capacity an excellent earner, better not to loose him. Hell, he organised the Lufthansa Heist. With regard to Tommy as Henry points "it was for Batts and a whole lot of other things."

2. Don't know the answer.

3. Batts wasn't expecting to get clipped. As a made guy he was considered untouchable - no punk
associate would be expected to dare take him on.
He seemed relatively comfortable in Jimmy's company in the movie and was probably unconcerned about other members of his crew not being there.