A coup by high officials might be possible, but not a mutiny or revolution. They are too brain-washed for that.
No they're not. They may think that their great leader is their god, but you know what they do
know? They're starving. They have some of the worst lives in the world. And I know they're brainwashed to believe that the NK government is doing the best job ever and it's the dirty imperialist westerners who bring them all their woes, but that propaganda will flow right off of them like water as soon as they're forced to march to war and die. Maybe the hardcore elite soldiers handpicked by Un will fight to the last, but the average farmer drafted into the military will not be so keen on dying for something like that.
Also, the NK people are not as brainwashed as you'd think. They're scared. Really scared. One reason why Japanese citizens were able to be brainwashed so easily during ww2 was because they actually had good lives, and the quality of living in Japan was actually pretty high at the time. How easy it was to believe that your great Emperor had provided for your every need every step along the way. In NK it's quite the opposite and the illusion wont last long after real war breaks out.