a) Canada, Germany et al are complicit because they know that NK is a despotism and that NK uses science to develop WMDs in contravention of international law.  But China is the most serious violator of the ban of transfer of technology to fascist NK.
b) China supports NK's arming of Syria, Pakistan, Iran, and numerous despotic African states.
c) China could halt NK's WMD program quickly simply by denying NK oil and money laundering facilities. But NK is useful to China, so China doesn't.
d) The US did not use NK as a "pawn" in the Cold War.
e) How did treating Hitler, Tojo, and Mussolini with appeasing "respect & politeness" work out?
f) The US has given NK significant aid and saved millions during NK famines.
g) FYI, NK now has ICBMs capable of hitting Denver.  And NK has hydrogen bombs.

You have a fundamental misunderstanding of international law and fascist dictatorships such as NK.

Your appeasement strategy for totalitarian thugs will bring the same result as it did in 1939.