Well I agree with all your points, Howver i like being honest, so i will say i disagree with one of your points:
"Why would Japan favor a Communist Nation (China) over another Liberal Democracy (USA) ?" China isnt a communist country anymore, not by a long shot.lol truth be told its even more capitalistic than some western countries.lool Its communist only in name.
Even if it was a communist country, it has nothing to do with japan favouring it over a 'democratic' U.S . In geo politics, theres no such thing as allying with a nation because of democracy or authocracy or dictatorship etc. It all has to do with interests and historical issues/situations as well(Japan came under the U.S due to it lossing the second world, not because Japan wanted to.lol).
This can also be seen in Indias case, India has been a democracy since it gained its independence from us over 60 years ago, but still it allied with the worlds most dictatorial/communistic country the U.S.S.R . So we had a situation where the worlds 'largest democracy' was allied with the worlds most powerful communist nation.
While the worlds largest communist country(China) later split with the worlds most powerful communist country U.S.S.R and allied/partnered with the worlds most powerful democracy the U.S during the cold war in the late 60s. Same with 'democractic' U.S(and its junior partner Japan) now trying to charm communist Vietnam into its laps against China.lol
So my point is, alliances has nothing to do with demcracy or communism/autocracies etc. As far a country interests go, thats all that counts. There a no friends per say in geo politcs, only interests. Tommorrow Japan might switch sides if its interests doesnt match with that of the U,S anymore. Thats how things go, no surprise/crime in that.