What do I do if I don't like a minecraft kids YouTube channel and he threatens to dox me and release my personal info on discord server?

What a kid can do?

If you don;t like his channel, don't go to it.
Ignore it.
Don;t watch his videos and just stay away from it.

That kid threatens to dox me

Ignore it, and do not go online again for 3 months.

Screen shot all the threats for evidence and report him.

Doxes only make people get to know you more. He might leak your name and address. Anyone can walk past your house and get your address.