Just being realistic. NKorea has demonstrated what is likely a non-deliverable device, and it was a fizzle. Early designs are quite large and heavy, on the order of 10,000lbs, and there's no reason to believe that they've achieved much in the way of miniaturization. None of their military aircraft can deliver such a payload, to my knowledge, and a scud probably wouldn't be able to lift it off the ground.
Despite their numerical superiority, DPRK forces are no match for the ROK's all weather airforce, modern weapons systems, and the most comprehensive defense in depth system ever devised. Survivability of DPRK forces approaches zero in any sort of attack scenario. Leaving their fortifications to attack across the DMZ would be suicidal. As I offered earlier, they're entirely cognizant of that, and of the consequences of using nuclear weapons against a US ally, assuming they could even deliver any. The only scenario where they have nothing to lose would be if they were in imminent danger of being overrun, and that won't happen unless they attack the ROK.