I think the sanctions with China cooperating is more important than the bluster. Kim fucked up when he got too aggressive with his tests and his threats, especially after his purge of China friendly people in his regime in the last year or two. It could be argued that China only agreed to the sanctions because they were worried about Mad Dog Donald starting a war on their doorstep, but China had been losing patience with him for a while.Thinking back... at the time... I was laughing at Reagan when he said "Tear down this wall". I thought it was stupid bluster. Well... most people don't think like me. Lots of people react to bluster and it can incite change.
If Kim caves, it won't be because he is afraid of war, but because he is afraid of not being able to afford keeping his supporters happy. I suspect he will do his best to draw out the talks as long as possible, get as many concessions as possible for staying at the table and not conducting tests for a while and ultimately not giving away his nukes.