Cutting a bullet, as well as an iron ball from a musket, is indeed possible - of course, having the speed to react to it is a different story, but that's not what you wanted to hear, right?

Anyway, muskets don't have the caliber to break a steel sword. Also, due to it's own velocity, the moment it comes in contact with the blade it effectively cuts itself - the blade just helps with that. As for the two pieces, because of the impact, the direction they split will go in a wide angle - where they land is unsure, but it's definitely going to be far from the one holding the sword.

I hope you don't mind my commenting, you did ask :)