What’s been done to the North Korean people since the 1940s under the Kims has been one of the great crimes against humanity imaginable.
Reintegration is going to be almost impossible since the people themselves are so different. The Southerners are living in a first-world culture, educated and well-nourished. The Northerners are impoverished, living in a gulag-state little better (and with less freedom) than those in the stone age, and are so malnourished, that has likely caused mental deficiencies and stymied their physical growth and stature. Just a horrible situation.
Yes it has. The huge numbers of people murdered by their own governments boggles the mind, and If you think that is bad, wait till the end times of the book of Revelation. That will be a period of slaughter that no one can begin to comprehend. God will get His revenge on them, and it won't be pretty.