Hi Darkman,
Some of the optional rules are not completely "baked" yet - so I apologize if some of the rules concerning them are a little confusing:
Regarding air-base attacks: I think your question has to do with AA guns? If so, AA guns are always allowed to fire at air units flying over their territory to a battle per the rules - this include airbase attacks.
New Japan homeland value: It would fall into the 6 or more category - so they could build 2 factories - but it would allow the US to draw more cards as a trade off.
Soviet event: Correct: If the Germans fail to take out Poland completely in one turn, the Russians are left with a less than flattering impression of German capabilities and get to draw a card.
We have been playing with the optional rule on damaged ships for about a year - so I think it works pretty well. In our playtest group, there has been a lot of discussion regarding Japanese carriers. As a good compromise, we decided they should have two hits like cruisers - (so after one hit, battleships and US carriers have a 1 in 6 chance of sinking. Japanese carriers and Cruisers have a 2 in 6 chance of sinking). Everything else is the same.
Does that make it more clear?
Looking forward to the next round of after action reports from Germany!
Mark