That said...
I would not melt North Korea, though I would use tactical nukes wherever necessary on military targets (without much regard for the civilian populace) and decimate anything approaching infrastructure (civilian or military). In other words, bomb them back to the Bronze Age, while asking China, Japan, Mongolia, and Russia for assistance. In the forthcoming speech about it, I'd note that the US reserves the right to glass a country that attacks us with nuclear weapons, but we are not compelled to do so and have not done so in this case out of deference to Japan downwind and in recognition of the oppression of the people of North Korea.