What are the laws about Jews eating rice on Passover?
Ashkenazi Jews can't eat rice on Passover as it's kitniyot (according to Rabbi David Bar Hayyim they can in Eretz Yisrael though).
Sephardi Jews can eat rice on Passover.
If the father is Sephardic, then does the individual follow his father's traditions?
Yes, you go according to you father's traditions.
What does authentic Judaism command?
If we knew that then there would be no difference between the Sephardi custom and the Ashkenazi custom. There would only be one custom.