1)  Hussein used chemical weapons to kill thousands of Kurdish civilians.

You are absolutely correct about the horrible carnage of the Iraq war.

But the issue here is the DPRK's non-stop threats to annihilate the RoK, Australia, Japan, and the US.

Hussein never made those kinds of threats and he never had that capability.

2) Again, it is 2017 and the DPRK clearly has WMDs, the capability to deliver them, and the will to do so.

Your skepticism, given the lack of WMDs found in Iraq, makes sense for judging Bush.  But this is an entirely different situation.

3) Yesterday the DPRK clearly was not lying.  They launched an ICBM capable of hitting Denver.  
We know that they have detonated at least 5 nuclear devices.  They are not lying about that.

The DPRK regime has been entirely devoted to war and settling old scores with some South Koreans, Japan, and the US for the last 64 years.  Hussein was surprised by the US attitude in part because the US had been an ally
against Iran.