I don't quite know the rules of a Taekwondo match but I'm a black belt in karate with many titles so I guess I can add some general advice.
It's a lot easier to score with punches (through my personal experience of going to competitions, people tend to score a lot more with punches than any other type of technique).
I do like his speed but he has a tendency to lose balance (I think because of that speed when he throws multiple kicks). Against better opponents, it will most likely be his downfall. To get around this (after previously having this problem myself), I recommend going back to basics and breaking down every point in the technique. You never know, he could find out ways to improve them.
As for the fight itself, your uncle was quite obviously the better fighter. Very one sided.