The aid is not for practical reasons, the PRC has aided the DPRK for decades. Its out of legitmate friendship.
The bilateral talks failed because Clinton signed a bad deal, not becuase they were destined to fail. A better foreign policy team could have gotten it done. In any case, all we should hope for is a holding measure. The final solution will be to bring about the collapse of the DPRK from within. We just need to hold them off for a while.
I think the relationship was friendship 30 years ago, but now it is out of necessity. China has evolved, North Korea has not. I'm sure some of the old guard in China still like NK, but most of the leaders probably see it as a dangerous burden.
Bilateral talks could lead to "progress" and six-way talks will not--I think we agree there. I also agree that "holding them off" is a good strategy for the time being. I am not sure that any progress we could make in bilateral talks would benefit us.
Perhaps if we suggest to China that a nuclear Korea is a threat to our economic investments in the area (i.e. we may "re-examine" our trade status with China) then maybe we could prod China into putting more pressure on North Korea.