Jaw-jaw is always better than war war. Besides, my guess is Kim will only use this type of weapon if his regime is threatened militarily. The country is always one bad harvest away from famine so this is simply an exercise in extortion for the usual items such as food aid and oil. 

There are many economic sanctions that have not been applied that could seriously damage the North's economy. For example, consider that countries or individuals that help North Korea do business have not been subject to “secondary sanctions” that would further isolate the country as was the case with Iran. 

There is also the matter of enforcing existing sanctions. According to the Economist, China is the buyer of 99% of North Korea’s coal sales and it stated in February that it would suspend all further coal imports. Yet North Korean vessels have continued to dock at China’s coal ports.