I could not see China accepting a strong US backed country camped on one of its borders.
It happily supports despots for geopolitical reasons Burma being an example. It has happily watched the north stave its people and not interfered.
If war broke out and the north looked like going down then China would certainly enter the fray. In some ways the north's actions shows how confident it is in China's support.
That's probably true, but with the amount of US debt they hold I think if you expect China to rush headlong into war with the US I think yu'd be very mistaken.
You can bet the Chinese have been supporting and encouraging Kim Jong all the way, despite their staged public protestations. Nothing would make them happier than to provoke a conflict with the US. They've a huge obedient military and they're just itching to exercise it against a big opponent. Underlying all this scheming and subterfuge is a deeply ingrained inferiority complex. Even if they ruled the entire World (which sort of looks a possibility in the future), the Chinese would still feel inferior to the West.
I don't know about this.
If North Korea believes this I expect they will be in for quite a shock on two fronts. China will not write off all the money it has loaned to the US (by far the biggest lender) let alone most of it's overseas investments, which will be the end result if they declare war and while China may have the man power, the US and it's alies have far superior air and sea forces.
If they declared war they would have to expect to decisvely win... which the deluded North Korean Nutters may, but China is certainly much more realistic in it's military capabalities. I expect it is more intent on winning the long term 'économic war' where it already has the upper hand.
Also, I don't see Obama as the type to rush to war, let alone even wanting it atm.
But having said that, if I was the US and North Korea kept beating the war drum and the shelling of the south gets worse... I'd expect a UN warning first... then I'd be planning a strategic, secret, no notice massive air strike on the leadership of the north and key mititary positions, as I'm sure they have contingency plans for. It is a classic case of an army that would be like a headless chook with the top few echelons taken out and China caught on the back foot and more vulnerable if it declared war.
You also have to remember the amount of international humanitarian aid going to the North. If a state of war was declared this would dry up in a flash leaving the population and much of the military after a short time, starving, weak and unable to support the war even if they wanted too. Is China in a position to fill the void as well as go on a war footing... I don't think so.