Part of the problem may be the money you spend on minor ICs, and that you let the UK player build them on islands where they don’t belong.
If Japan doesn’t get of to a big start, they are going to have a rough go. I would hope that after turn three China is practically out of business, and by turn five Calcutta is in dire straights.
Have you tried the J1 approach or are you afraid to go big until J3? The US boost is not as bad a 40 IPCs sounds, because the Japanese player gets a lot of compensation in some of the little targets they pick off in the first turn. The PI and Hong Kong are worth about a 20IPC income swing, for example.