I think this is mostly right, but there is still some room for concern. First off, those anti-missile defenses have never been tested in anger and we can't be 100% sure they will work. (I'd love to think we have an effective boost-phase defense in place, but I gather that's not going to be a reality for a few years yet, at best.) Second, what I think Kim really wants to use those nukes for, besides leverage in the sanctions discussions, is to pry apart our alliance with South Korea, by making it too dangerous for us to come to their aid once NK attacks Seoul. Even with Pyongyang flattened, there could still be launchers hidden in the mountains and one of those rockets might get past our defenses. Would you really want to risk Seattle or San Francisco or even Honolulu?

On the other hand, I think everyone except possibly Kim and his minions wants peace and stability on the Korean peninsula. The Chinese certainly do, and I think even the Russians, though they have less at stake, would not want to see war break out — certainly not nuclear war, which would endanger Vladivostok. What I don't know is how badly Kim wants to conquer South Korea. He likes to argue that his nukes are for defensive purposes, and that's not unreasonable under the circumstances, but the problem is that they can be used offensively as well. What I would like to see is a peace treaty that obliges not just us and Japan but also China and Russia to participate in obliterating North Korea should they attack South Korea or anyone else.

That sounds like a pipe dream, but consider this. We could provide South Korea with nukes. Yes, it would be in violation of the Nuclear Non-Proliferation Treaty. (I wouldn't suggest abrogating the treaty altogether, but it has clearly failed its purpose in this instance. A case can be made for restoring the regional balance of power.) We shouldn't bluff, but a credible threat to nuclear-arm South Korea might bring China and even Russia to the table.