Update. China has pretty much captured my coal island (not that I really need it anymore)...except if they bomb my railroads, there won't really be a way to get those rebuilt. Still, I have drafted enough infantry up on the island that it is taking them turns to get through all of the defenses. My other island with oil+rubber+iron is well-protected, relatively, though closer to the Chinese mainland, so it's experiencing more bombing runs.
There's a little bit of war weariness now, but it's not bad.
I've elected to go minimum science on Fission to gain +1200 GPT. This helps me to both save gold for a tech steal (I think China will research Fission before I can) and to buy many infantry, fighters, and tanks to ensure China can't just walk onto my mainland without a heck of a fight.
It seems this game thinks of new challenges to throw at me to ensure that my victory won't be easy, just when I think I've put the game away. I think I can, I think I can.
edit: Signed America + Arabia + Zululand against China. I expect America to be wiped off the face of the planet but it's worth adding various distractions for China so they don't concentrate all their bombardment on my lands. My spy planted in China also tells me that China's force is mostly concentrated in their vast quantities of Cavalry, Infantry and Guerilla (1500 combined), neither of which can really do anything to me, at least on my main two islands. By the time they get Mech Infantry and Modern Armor, this game will be over. They don't have many transports and they aren't really building huge quantities of marines either, thus alleviating some of my concerns.
edit 2: note to self: game crashed @ 1710 AD and had to restart turn
note to others: do not fight superpowers on Sid level, intentionally or unintentionally