If Trump and the Japanese want to get China to do something about the dog eating nut job all they have to do is hint that the Japanese will probably have to develop nukes in response to the Norks and their nukes and missile tests. Also hint they may have to consider the South Koreans doing the same thing. See how long nut ball keeps breathing.
Japan already has nuclear weapons technology and has for a long time. If they decided it was necessary to thwart North Korea - or China - they could deploy sophisticated fusion warheads very quickly.