Difficult to predict what might happen if people panic but I suspect the Chinese have put guardrails around him, specifying what would be unacceptable and incompatible with their support. Doesn't mean that a desperate panicking person would adhere to those limits.
This is a slight presumption. Xi Xing Ping 'support' is riddled with caveats including an insurance indemnity: in a scenario where Russia run out of credit (that point must be looming large?), Russia may have to cede land.
Plus: China is not giving weaponry free. This was mainly a channel for purchase outside of international sanctions and China has already expressed concern to Putin about their global standing regarding this after numerous dignitaries (Starmer included) have put pressure on Xi Ping. China stands to win if Russia looses or succeeds, so the outcome for them sits on an uncomfortable shelf for Putin.
If the Chinese pull the plug, Putin is triple f*cked. The plug will be pulled if the debt looks toxic; no amount of loyalty will be sufficient to generate leniency. Think of China as the Bank Manager.
This bank manager pledged support initially as Russia looked to be an economic and political partner but now the partner is struggling, so what to do. They cannot support a whole regime in a country that is being hammered.
Trump has singlehandedly diminished US interests and influence. I do not know whether the Chinese view this as a long term consequence or not but the fact is, China's power has been bolstered to the extent that the outcome of this conflict no longer carries the same weight. Their attention will turn towards resource procurement and we do not know the extent that Putin is willing to go to in order to secure weaponry and support. I can safely presume Putin would be desperate but if the coffers are already running dry, he has weaker and fewer cards to play.