I'm not convinced this analysis holds up to the numbers. China imports around $135B of food per year. Before the war Russia was exporting around $35B. Admittedly a lot of the Chinese imports are luxury foodstuffs but that's still a big big gap. China can't feed itself, even with Russia's help. This is a recurring problem throughout China's history.
I think you underestimate the importance of "plasticky trinkets." Exports are the backbone of the Chinese economy. Without them it can't afford to import food, and millions of Chinese starve. If China declares war and isolates itself so that Russia is its primary remaining trade partner, millions of Chinese starve.
The biggest importers of food to China today are the US, Brazil, Australia, and a handful of Southeast Asian countries - basically that's all gone if China goes to war or isolates itself in some other way.
Now I mean sure anything can happen in a war and the CCP might very well choose to let millions of Chinese starve, they've done it before. My point here was that isolation would inflict terrible and permanent damage to China. A war is unlikely to happen in the first place because not only is this damage so great, but China would probably lose any battle that wasn't very close to their home theatre.
By the way, Chinese food security is a great topic for illustrating how dysfunctional they are as a country. Here's an article on the topic - https://www.cfr.org/article/china-increasingly-relies-import... - basically they don't have food security, achieving it is one of their top priorities, and they are failing to achieve that priority. The cost to grow soybeans in China is 30% higher than in the US, and the yield is 60% lower!