[bob jenkins]

Originally Posted by TwoBits

May be picking nits here, but in the OP, it doesn't say that the runner actually is trying to score, but just taking a long lead as if he is going to break for the plate.

In youth games, I've seen very long leads at third base, particularly when the pitcher is in the windup position. Sometimes it is the type of leadoff described even before the pitcher has begun his pitching motion.

Still interference by the batter? If so, would the runner at third be declared out with less than two outs?

Not covered. You could decide that it's a violation by the batter ("weak interference") and by the pitcher (delaying the game by throwing to a fielder without a play) and just reset everything.