Here are suggestions of how to solve the North Korea problem without a shot being fired
In the mid-50s there was a NATO like organization named South East Asia Treaty Organization, which was formed for a common defense against the spread of communism in that part of the world. The organization as long since been dissolved.
My suggestion is for the U.S. to lead the way to reconstituting SEATO with member nations that feel threatened by North Korea, including Japan, Australia, South Korea and New Zealand, etc. A re-formed SEATO would not only become a common defense organization but one that could use it's common economic power to pressure China into reversing North Korea's nuclear and missile programs. China may well want to keep its trading partners happy as opposed to North Korea, which is a burden to it's economy
Then, spread a rumor that there is an offer on the table of hundreds of millions to be spread among officers that succeed in a military coup to depose "The Dear Leader" Kim Jong-un. He will become so paranoid that he will begin a "off with heir heads" campaign within his top military leadership.