The airbase is a great idea. This also allows you to Strat Bomb India (and strike fleets all over the money area) though the wisdom of doing strat bomb will depend on how hard the Allies make India to take.
The remedy to the UK declaration and rush on China is to threaten India. UK has to step back or be annihilated–you can demolish him with all your planes and boats anywhere on the coast.
The problem that is going to emerge is that you can’t let the USA blast SZ 6 (even if he can’t take out any of your major fleets or land on Japan/Korea) because if he can kill what’s there or blocking it, he may be able to take Iwo, land in Russia or worst, cover SZ 6 from a distance, which means he can destroy the new units you lay, unless you join up with a massive relief fleet. SZ 6 is the node for all your transports–if SZ 6 isn’t safe, your deployment and momentum stop.
He can also noncom into SZ 6 or the squares below that, blocking your ability to relieve your homeland and tearing Japan in two. During a KJF, once japan has no SZ 6 fleet, it may not be able to coalesce what’s left into a sea defense, which leaves you with just a land turtle of infantry and fighters. This paralyzes Japan because they can’t deploy their strength and all their efforts have to go into a homeland rescue.
If he takes Iwo, he can strat bomb you. Japan is vulnerable esp. on turns 2-5 because its big fleet and airforce are busy trying to kill India–after that point they can split the fleets and have half of it come home. If he gets to 50+ income, he will be able to build with USA, at parity, considering all the air assets and kamis japan starts with, and the difficulty of any direct invasion with us transports.
You just have to be careful that the USA doesn’t make SZ 6 into a dead zone before you can recall your capital ships.