Something I wrote in a discussion elsewhere, seems relevant here:
I see China's support for North Korea as very much like US support for Israel.
It is long-standing policy and changing it would both upset some folks at home and involve completely unacceptable loss of face for the supporting nation. Ain't gonna happen.
The supportee has a long history of doing various stupid aggressive things, all in their view fully justified since they have obvious and powerful enemies. The supporter can express regret, call for everyone to calm down, have talks with the other side, et cetera. However, they cannot really control the supportee. Influence, one hopes, but not control.
With the powerful foreign support, large military, and nuclear weapons the supportee is unlikely to be knocked out in war. If there is a war, it is likely to be messy.
We can hope some sort of political change solves the problem eventually, rather than the whole thing blowing up. In the case of the Israeli-Palestinian conflict, there's at least some evidence of sanity on both sides. There seems to be less evidence of either sanity or potential for change in the Korean situation.