For 1, if Japan is to pressure the US, they need to attack on Turn 1. Japan simply can’t compete with the US at the start. It’s 26 vs. 52 first round spending, and after that, about 39ish (assuming no DEI gain as they’re pressuring the US) vs 80 or so on Round 2. While the US money never really goes up, Japan’s won’t increase by much if you’re not going for India and the DEI really fast.
The US just needs slow and steady Naval buys, using a good mix. Look at their transports and how much land units they can get to the WUS. If they have a bigger navy then you can plop down in a turn, then buy mostly planes first, then place them on carriers.
With Japan focusing on the US, India should be relatively free to take the DEI and grow in size. They can either build up their own navy, or help China. Either does well at slowing Japanese growth.
In the end, I think Japan will spend too much effort against the US for less gain than in other places. They won’t close the gap against the US’s 80ish income, and that starting fleet won’t last forever.
And I’m not sure what you mean by “liberate the UK”. You’re assuming they’ll lose. From UK1, buy 9 infantry. Turn 2, with NO money, buy 8 Inf 2 Tanks. If Germany goes all in for transports, it’s still a 50/50ish shot or less. Forget Africa until after sealion fails.
Russia should also buy mostly ground troops to prepare for an eventual German assault. The good news is that any Sea Lion is extra turns for Russia to prepare.
Also, if Japan is focusing on the US, they’re putting less on the Chinese mainland. It might be a good idea to consolidate your 18INf, and then on RUS 2, attack Manchuria and Korea. Put more pressure on Japan while they’re trying to do the impossible of attacking the US.