I guess I am completely different here but the cat is out of the bag he has been allowed to advance to far unchecked.

At this point I think we build South Korea a short range nuclear weapon and place it just south of the DMZ with just enough motor to reach the China border. NK is on the verge of or has become a nuclear nation. Therefore the playing field should be level arm S.K. and see how quick China puts pressure on NK. We should publicize the hell out of this let it be known S.K. has this capability and that once NK is disarmed we will disarm S.K. in turn

China wants a divided Korea to limit competition in the region, this will balance power and provide both countries with equal detriments