The hard bet is that 1) while evil, Kim is not irrational, 2) Kim likes his waterslides and harems, and 3) Kim will not commit suicide.

If Kim strikes SK or Japan or US, it will be the last thing he did. Sure, tons of innocents dead. But Kim and his fiefdom dies too.

I think Kim is bluffing. Worst case scenario IMO is not a direct strike nuke icbm but a detonation in the magnetosphere to EMP North America. Would do more lasting damage. Still suicide.