The batter has the right to hit the ball, and doesn't have any responsibility to get out of the way in most cases. If the umpire judged that there was time for the batter to move, then they could call interference. However, in most instances of a runner stealing home there is not enough time. Yes, the runner could go through the legs of the batter. I know one college coach who use to teach it that way.
If I can recall those dadgum high school rules.....If a runner is hit by pitch, then it's an immediate dead ball, all runners advance one base, run scores......unless it was the 3rd strike for the 3rd out. I think that's right, but high school rules seem to change almost yearly and a lot of the times they are just plain screwy.
I'll wait for corrections.