Legitimacy of DPRK nuclear threat

Everyone has no doubt heard about the North Korean nuclear test that has sent shockwaves rippling around world governments. However, the actual threat imposed by the weapons of the type tested by the Koreans seems to negligible. It is known that they do not possess a weapon small to mount on a missile, so that threat can be discounted, for now, but that would leave only their Air Force to support their deterrent using gravity bombs. Furthermore, their only possible aircraft to carry a large bomb would be the 80 or so Il-28/H-5s which they aquired in the 60’s. These subsonic aircraft would be easy meat for the any modern aircraft flying CAP over the South, of which there would be many. So it seems that the North’s test doesnt pose much of a threat, due to the unsophisticated nature of the DPRK bomb, and the technological gap between the respective air forces. Am I leaving any possible scenario out? Could the North have any other means of delivering its bombs?