I think if China threatened to attack Russia economically on pain of immediately leaving the Donbass, Putin would have 0 options but to follow the demand.
That would be cruel of China.
Ukraine makes no secret of the fact that it will carry out ethnic cleansing in the Donbass and Crimea once it regains them.
I even saw a post on Twitter, a French TV channel, where they were discussing the future ethnic cleansing of Crimea.

