They have a gigantic strategic oil reserve (it has its own Wiki page!), and I would assume the same for food as well. I'm sure that Pakistan and especially Russia would be happy to help with them as imports as well, maybe not as much as they use in a given year, but enough to help out.

Most of the simulations for a naval war around Taiwan predict that it would be over in a few days, maybe weeks, but not long enough to really draw down those reserves.

Most importantly, it's really not realistic that the US Navy could prevent the rest of planet Earth from providing goods to the world's largest trading nation. Our navy isn't big enough, for one thing, but the economic damage to every other country that imports into China makes this blockade idea pretty unrealistic. I can't even imagine how much inflation would spike when the world's factory can't export for a few weeks

The US Navy is big enough to impose a fairly effective blockade on China for an extended period. All they have to do is drop a few mines near Chinese ports and shipping labels. Marine insurers will then decline coverage for all merchant vessels in those waters, making it impossible for neutrals to operate. The Chinese could still accept the risk and run their own flagged ships through but overall trade would be greatly reduced.

This is incorrect. China is self sufficient in calories. Chinese citizens would have to eat less meat and less fish, but they would be very far from starving.

China has a border with Russia, and gigantic strategic oil reserves. They are not going to run out of oil. Maybe ration it initially, until enough can be delivered from Russia.