Hi Dan!
I'll try this one ASAP, but I tested your first scenario as is and even with your basic deploy, the Chinese have nearly overrun the island and plunged into the Pacific ocean, standing on their brakes!
And the Taiwanese fight like, well, tigers! The test was IA vs IA, and on turn 10 they had not a single infantry squad destroyed! At first sight I would never have thought they would hold that long!