Things I learned about fighting China:
1: Try to control them not conquer them. Contain them from getting to the coast. Always be able to take the road back.
2: I have found that an IC in Kiangsu can work. I always have some land based Aircraft that are designated for Chinese attacks. Spend what Chinas income is as a rule of thumb at the IC. I usually buy 3 mechs a turn. Movement to the road is quicker and supporting Aircraft make most fights manageable. Going transports can work too. Just a lot harder logistics. Japans Achilles heel: getting troops to the land.
3: Dont be afraid to slam a chinese stack with just Airforce!! Especially early turns. Kill that flying tiger whenever you can. The payoff is much greater than the potential loss of aircraft.
4: Fight China with the end goal of getting to India! Once you have Calcutta the road is closed! Do not let the allies coordinate! Russia cant be helping china or UK reinforcing them. Keep them isolated from each other.
5: Know when to leave them be. Concentrating on China to much can hamper all the other objectives Japan must accomplish. Dont let it be a money pit.
Just some thoughts on fighting China. I have yet to play the perfect Japanese game but i would suggest giving them another chance. They are a blast to play. Sometimes you have to understand what your role as Japan is going to be. They are sometimes very dependent on what Germany does or how Germany is doing. Have fun!