Sure, "things." What "things?" No one, I think, will gainsay that the North's nuclear capability is something to take seriously. And everyone in our neck of the woods pretty much wants to do something. But again, what? In a purely utilitarian analysis, there is far more bad attached to any direct action than there is good, especially when you take into account the limited likelihood of a real success, if you define success as eliminating North Korea's nuclear program. That, I'd argue, can only be done by, well, eliminating North Korea. And, no, they aren't going to sit back and let that happen. As wretched as the North's posturing and threats are, the calculus shows that that's a better situation than full-on war on the peninsula.
I agree that China has been, shall we say, ambiguous and ambivalent in its restraint on Pyongyang, and for the reasons you describe. But, just as with the PRC's position in the South China Sea, no one is going to be able to budge them from their desire to have both a buffer in North Korea and a true sphere of influence as they see it. Beijing, as I understand it, has a problem with North Korea. They need the state to stay intact, and hostile to the West, yet not _too_hostile, so that it provokes its own destruction. They also are very, very nervous about nukes on their borders, especially those controlled by a less than predictable and probably unstable leadership. So what to do? All the steps you outline would self-defeating, because all the North would have to do is implode and voila, tens of millions of refugees, a power vacuum, and the ROK on their border in all likelihood. Pyongyang has been blackmailing everyone forever, and is not likely to change, because they have the trump cards.
Personally, it galls me to no end to have to allow the North as much leeway as we do, but until someone shows me a viable alternative that is not worse than the status quo, I think we have to continue to do pretty much what we are doing. Pressure Beijing to find a way to ease the Kim's out, bolster the ROK, isolate and condemn the DPRK, and prepare for the worst if necessary.
My own plan would be for the PRC to offer the entire leadership cadre of the DPRK the equivalent of dachas on the Black Sea, somewhere in China, with all the cognac and cigars they want, in exchange for a demilitarized but Chinese-dominated North Korea that would still be a buffer but would cease to be a military player on the peninsula.