The North Korea population is "content", mainly because they know no other way of life. There is little or no contact with the outside world. What they do know is that 100% loyalty to the "Leader" is required. The option is death. The people of NK have seen high-ranking government leaders and even relatives of the "Leader" executed in public for things a minor as dozing off during a speech.
The NK military is a force to be reckoned with. The military knows two things. First, they are brainwashed into believing that no other force in the world is greater. Therefore, they have the confidence they will succeed in any confrontation. They also know there is no option other than winning in battle. To lose... to surrender... to return to their own country without a victory would mean public execution. With those things in mind, the military are not afraid to use nerve gas or nuclear devices to destroy an enemy... even if it is a suicidal mission.
Kim Jong Un was schooled in Europe and understands the forces he would be up against should he cross a threshold. The longer he stays in power, the more he has a need to display his "greatness" to the people. So far, those displays have been either execution of his own or military exercises that provoke but do not invoke retaliation.
People are starving to death in the streets of NK. People are hauled to concentration/work camps in NK and are never again seen by family members. The population lives in constant fear of their leadership... a fear that is often construed as respect. There is simply no means of the people rising up. They know no other way of life other than living in fear. I still believe that Kim Jong Un will make his misstep with China and they will be the one to effect a covert mission whereby he will "go missing".