Wiskey, my big problem with your scenario is that the DPRK is incapable of taking the South, regardless of what the Usurper does. It has beeen at least a decade since the ROK’s needed US military help to deal with hte north.
To many people underestimate the ROK’s. In ’50, they were better then the US Army. They moved farther, faster then the Army without having their own tanks, air cover or even transport at first. Once the got trucks they really took off. None of the Marine landing planned after Ichon happened because the ROK’s moved fast enough to take the proposed landing sites before the Navy could get the Marines there.
Granted, the Rok’s didn’t do all that well when the Chi-Com bugels started blaring, but they did at least as well as the US Army. They held the flanks long enough for the Marine to fight their way out of the trap at Chosin.
Today, the ROK army is the equal of ANY nation in the region.
S. Korea is a major industrial power, the Equal of most European nations. Their economy is ranked either 13 or 14th, depending on whose criteria you use.

http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)

Note that they are right behind most of the European nations. Ahead of Canada, Turkey AND Australia.
the DPRK, on the other hand, is not even on the lists. It has a GDP about the same as the local Wal-Mart. If it was an American corporation, it wouldn’t be in the top 500. Even under today’s less then vigorous economy.
No, either Kim got a batch of bad ‘rooms or he is playing the mouse that roared game. Only David Niven is dead. Kim needs to be.