They don't need Russian support to attack Taiwan and Russian economic support is meaningless. They won't do it because there is no incentive to. The US has to bribe them. Think of China like an evil corporation. They won't do anything except for their own best interests. Like Facebook with nukes.
I don't think adding the tag of "evil" in front of corporation is necessary or helpful. Corporations are selfish and aggressive enough already. Nothing about China's geopolitical plotting is anymore evil than the US or Russia, regardless of what ideological non-sense you use to justify any corner.
Russian support won't come in the form of money or weapons. It'll come in the form of shutting off gas lines to the EU or invading the next set of non NATO countries in the EU, forcing the major military powers of the EU and NA to decide between protecting Europe or protecting Taiwan.
China can't invade Taiwan without Taiwan blowing up the Three Gorges Dam and wiping out 1/4th of China's population