The Pitcairners aren't exactly a country. The UN calls them a non-self governing territory under jurisdiction of the UK.

I think Bhutan is the most isolated real country. NK is second. You'd much rather be a Bhutanese, though; by extreme contrast to NK, Bhutan is considered by many the happiest nation on Earth.

65? I thought that was well below the limit for a viable/self-sustaining gene pool.

NK gets millions of tourists every year (mostly Chinese).