The South Koreans happen to have a rather effective army as well. I sense a tendency to build the North Korean soldiers up as being 10 feet tall here. They aren't. As for their missile program, that is useful largely against Seoul and not much further south than that. It wouldn't be the first time that city had been reduced to rubble. Nor need this be considered strictly in defensive terms - remember Inchon. The North will have to consider the obvious counterstroke against their own territory because we've done that sort of thing before.
Personally I don't think it will come to anything like this. The North no longer has Soviet patrons. And if the Chinese feel compelled to cross the border again they can keep the place. They don't want it.
Other thing to keep in mind is there isn't a single soul in the entire North Korean military with any actual real large-scale combat experience whatsoever.
That matters.
Heh. Probably they are quite short from lack of good nutrition their whole lives.