"They might have hundreds even thousands J8, J11, H16, JH7 fighter and attack aircraft squirreled away."
Never mind the aircraft: what about the pilots?
Chinese pilots get about as many flight hours in one year as their American counterparts get in one month. If they're hauling equipment out of storage, they're doing the same with pilots. They'd probably lose over 10% per sortie just to accidents.
"If they go nuke in the Taiwan Strait and around Taiwan (but avoid Taiwan mainland) that will nullify US advantage at the same time make it difficult for US to engage nuclear."
But would the Chinese national leadership be willing to bet their personal survival on that assumption? US nuclear forces would most likely be targeted on known and suspected relocation sites for the Chinese government.
And you know this how? Personal inspection of flight logs? Or could it be, that disinformation, portraying lack of training, is fed to the West. "When you are strong, appear to be weak."