I don't think field behavior is a sign of riding behavior. I've had horses run around playing, bucking, kicking, etc, and then I bring them in and ride them and they are fine. Actually, I like to see them getting the sillies out on their own time. Better than holding back a hyper horse under saddle.
My friend even has a colt that she was worried might be a bear to ride because he had some real bucking fits out in the pasture (on his own time). He is in training now and is reported to be lazy!
I always think of it as them having fun, not as a threat towards humans.
Now the charging thing could be an issue if he is in fact charging. He should be respecting your space. I agree with smacking him hard with the whip.
I had a habit of "tapping" with my whip when working with my weanling (who wants to beat on a baby?) and it has come back to haunt me because now he is pretty desensitized to the whip and I have to whack him really hard to make an impression when he does wrong.