I don't think that Kim will start the war. All the rhetoric is directed to receive attention to his country and to achieve some political goals. Nobody can stand against the pover of the USA war machine.
It is true that no one can stand against the power of the American war machine. But an invasion of North Korea is going to be extremely costly for the US. My guess is that anywhere from 100,000 and 1,000,000 Americans are going to lose their lives if they do so. It is not like invading some small nation such as Iraq or Libya. North Korea is also very powerful.