You are right Roy. Israel, India and Pakistan all of acquired nuclear weapons since the nonproliferation treaty was signed. No weapons have been fired - yet. All it does is ensure the regime's continued existence. It is a defensive weapon.

There is no end-game for Kim except continuity of rule. He knows if he unleashes nuclear weapons the DPRK will be bombed back into the stone age. Realistically he can't even use it as an extortion threat.

The real issue whether Kim will do something irrational. Before 9/11 hijackers just took planes to another destination and made demands. 9/11 was a game changer. We had people willing to die to turn a plane into a weapon. 

Kim may irrationally decide he can win a nuclear war or doesn't care. Nuclear weapons in the hands of an irrational person is another game changer.