I'll say something on topic. I believe what we're seeing is Kim Jong Un showing that he's a tough guy to the remaining old guard and new fellas that he has running the military. It IS the NK army that runs shit in that rockpile and little 'Un, in the kind of move of strategic brilliance that you'd expect from an inexperienced 20-something, entitled, douche, decided to use alleged violations of the mourning period for his dear departed daddy to purge the upper and middle ranks of the NK army when he took over.
Unfortunately, he couldn't clear them all out so some of the older guys are still there, a bunch of new guys have moved up the food chain and little 'Un is needing to demonstrate that he's a tough guy to retain their support and show that it'll be business as usual in Best Korea.
In short, he's going with the tried and true mantra of: a fuck up can only be remedied by committing an even bigger, more colossal fuck up. Ergo, piss off the South Koreans, Chinese and Americans by acting exactly like the very thing he's trying hard to not be viewed as: a petulant tyro in charge of the last real communist dictatorship on the planet that hold the record for failing at...well...nearly everything (except failing itself).
My biggest concern is that with him artificially escalating tensions, the scene is set for someone doing something stupid and he's tough talked his way into a situation where defusing such diplomatically is almost impossible. Consider that he has new people in charge of some things. New people who may wish to demonstrate their loyalty to "dear Leader" (or whatever other ridiculous euphemism he insists his people refer to him by) by being even more "hard core" than their predecessors. So, maybe you get a South Korean fishing boat that strays somewhere near North Korean waters...and the local NK flotilla commander decides to sink it or worse, capture it and hold the crew hostage. The U.S. wouldn't be particularly effected by that...but the South Koreans would do their best imitation of nuclear, gangnam style apeshit over such an event. The Chinese want to keep the status quo (NK poor, backward but in charge and acting as a foil against SK, Japan and the US but not unleashing a tide of NK refugees across the Yalu into Manchuria) so they ring up little 'Un and say "hey man, cool it" and he (because he needs to assert his power) tells the Chinese the juche version of "get bent".
No way in hell do the Chinese want a reunited Korea next door under the new management of South Korea. The economic challenge such a country would present to China would be a nightmare for them. No way will the United States allow a reunited Korea under NK management as that poses a direct risk to ally Japan and it would de facto mean that the US bailed on an existing ally (SK). World markets would literally shit their collective pants at the thought that America may not honor their treaty obligations and into Great Depression II: Korean Boogaloo, we'd all slide as a result.
Further, America has no freakin' desire for The Kims to get their chubby little paws on an actual nuclear threat capability as long as they're running things like they do up north. They are indeed very concerned (and rightfully so) that NK would only gladly sell such a device to other enemies of western democratic governments like...oh...maybe an Al Qaeda who's on the ropes pretty much everywhere who might like to demonstrate that they're down but not out. NK would gladly accept hard western currency or specie for such a device and they'd do it at the drop of a hat, to boot.
What hopefully ends up happening is an internal coup by the military that sees little 'Un deposed but not assassinated where the successors immediately suck up to China and promise some reforms but not enough to allow the entire NK population to want to flee literally anywhere else. Un can't really back down at this point without some kind of perceived victory and we all know what would happen to NK if the little shit actually launched a missile attack of any kind whatsoever at anybody.