In that case, I see China and Russia to be an equal #2, with Islam being #1. As far as propensity to act, Islam would be #1, but that depends on the group or strain of Islam with the weapons.
However, as far as amount of damage and graveness of threat should the country act, Russia #1, China #2, North Korea #3, Iran #4, and so on.
That I can agree with. Your first paragraph is 100% correct. For your second I would like to make one adjustment - put Pakistan on that list, and probably number 1. Because if a WMD (particularly radiological or nuclear) ever goes off in the Continental US (or Western Europe for that matter), God forbid of course, you can be certain that somehow/somewhere there will be a Pakistani link. Guaranteed!