#1 is indeed an issue. Since a CV in the game represents 1-2 CVs plus escorts, then why cannot bombers and fighters be combines into a single unit? The single unit could have two ranges, one for escorted flight and one for non-escorted flight. That would solve this issue.
#2 It would have to depend on how close the LBA was to the battle. Obviously the closer the better . In War in the Pacific, there is a lot of randomness to LBAs helping out with CVs. Weather in the LBA base hex and along the path to the CVs, range, etc. Also in WitP, what does shows up, if anything does show up, is some percentage of the available LBA force. Even if you are just a few hexes away from the LBA base, typically a lot less less than half of the LBA force will actually show up. So unless you are in the same hex as the LBA base with CVs, you should not expect a lot of help from LBA. In all the time that I have played WitP, LBAs have never had a major impact on CV battles unless I was in the LBA base hex or just one hex away.
Also LBA forces were a completely different command for both sides. So LBAs would attack separately from any CV attack.
So in game terms I have no issue with this in WPP.
#3 The issue with China, as in the entire PTO is hindsight. It is not the Chinese units that are the issue, it is supplies/manpower for Japan. Once war broke out with the Allies, all major operations in China stopped as Japan did not have the supply/manpower capacity to support their offensive against the Allies AND China. So if Japan really wants to concentrate on overrunning China, and they should be able to, then they 'should' have to pay the 'cost' for that somewhere else in their Empire.
Again actual supplies, guns for the men, ammo, food, etc. was not an issue. It was the transporting of these things around was the issue for Japan. And it would have taken a massive amount of transports to supply Japan's men in China to have enough force to capture the country. Which of course would have meant that somewhere else was NOT getting these supplies since Japan's transport fleet was stretched to the limit as it was.
So it looks like there is no cost for Japan to do major offenses in China and they ae still able to go full tilt against the Allies. Maybe it should cost Japanese units in China double (triple?) supply cost to attack a Chinese unit. That might better affect the historical situation better than what you describe above.
Of course if you like the PTO, you should really be playing War in the Pacific AE anyway