As to the chances of the nuke working, well, you gotta ask yourself, do you feel lucky, punk? X-/
Edited to add: We are discussing here whether Iran wants nukes. Therefore what is relevant is that the Kims wanted nukes, even though they had the artillery-can-reach-Seoul deterrent already.
Ideally you want multiple deterrents, of course.
As to the chances of the nuke working, well, you gotta ask yourself, do you feel lucky, punk? X-/
Edited to add: We are discussing here whether Iran wants nukes. Therefore what is relevant is that the Kims wanted nukes, even though they had the artillery-can-reach-Seoul deterrent already.