The best description I've heard of N Korea is that it is a hostage situation where everyone (including all of the leadership) is a hostage.
I don't think that N Korea is suicidal, that said, I do think they are unreasonably sure of themselves. Trump is a massive wild card and he WILL overreact to any real attack on the USA (which to be honest is probably the right move). I am in no way concerned that the N Koreans will attack the US, but a city is a large buy in on that bet. If N Korea attacks the US, our best bet is to end the war instantaneous because any other action will force china to get involved resulting in WW3 and the destruction of the modern world.
China is playing double agent. They want the US to start a war so they can get involved end consequently take the US's place as top economy.