I hope that you all will indulge my late post on this issue but another thought came to my mind on this issue; especially after watching a spirited discussion about it on Fox News Sunday this morning.
Japan and South Korea are both regional allies and as such are de facto protected by our 'nuclear umbrella' but I was surprised to hear that neither nation is actually nuclear armed. That could fairly easily be remedied by the US. Not sure if this would help for us to do so in an immediate sense but it would certainly change the dynamics of our relationship with the Chi-comms and the Russkies in terms of putting pressure on them to solve this problem with their pot-bellied, god-less communist dictator friend in Pyongyang. Even the threat of our arming South Korea and Japan (or, perhaps, the Republic of China {Taiwan}, eh?) could change the situation.
Anyway, just a thought before I forgot it.