So far S.Korea is still friendly to China. No need to arm N.Korea, at least for now. Russians did help N.Korea a lot in history. It's time for Kim to do a favor to Russia as pay back.
By the way, N.Korea is not that close to China as most people believe. N. Koreans have a strong will of independence. Quite opposite to S. Koreans, who are totally tamed by the west. Pobably because democratic countries are easier to be manipulated by USA. Which is part of the reasons why US tries so hard to promote democracy all around world.