How big is polaris the north star?

none.its the little dipper that has the north star.the 2 stars at the end of the big dipper points to the north star.its name is polaris

Because the earth's north pole happens to point [very close] to Polaris.

It is currently but 5,000 years ago the North star was Vega. This is because the Earth's axis wobbles (precession) every few thousand years.

Polaris is called the north star because it is directly above Earth's north pole. So, if you find Polaris in the sky, that direction is north. Actually, Polaris is very close, but not exactly in line...

No, Polaris is part of the Little Dipper, or Ursa Minor.