Well I "think" I'll be in the best position to answer these questions.
Skipping 1 and 6, I'll start with 2.
2,3 I'd say this: In psychology, we have this thing called the recency effect, where the most recent effects is the most fresh in the mind. Japan's damages were the longest, with the duration of the invasion and the vivid memories of Unit 731 and Nanjing, therefore the anger still lingers. The earlier damages made the wound very painful already, but Japan's damages were the latest, and thus sting the most. In addition, it's the attitudes by the Japanese government which became the highlight and kept the pain lingering, otherwise it should slowly dissipate with time, as with the hatred towards others. I also talked about this in the Rape of Nanjing thread.
4. To me as an IR minor and knowing the past, the worst wasn't Japan, and I NEVER considered Japan as enemy or even a true threat. Not only not a threat, I see Japan as our most important neighbor, a cultural brother, and an ally to win back. I see the West as the dangerous one, because Asian cultures are slowly being culturally genocided and we are getting lost as we attempted to follow the West's footstep without knowing what's right for us. Japan already lost its national direction in the past, but luckily the culture is very intact, thanks to Japan's sense of national identity and cultural preservation. However modern lifestyle of materialism, consumerism, greed, etc, can eventually corrode the society for the worse.
I think MOST people in Asia are too unaware of the impact the West have in our cultures and societies. We Asians seek modernization, but we can't distinguish the fine line between modernization and Westernization, which is very problematic. Japan made this mistake in the past, which also led to the Imperialism. Western Imperialism was something origin to the West, not Japan, hence this is what I speak of when I say we can easily sidetrack, walk wrong, and screw ourselves over. Japan, in a sense, were big brother to China when it comes to modern IR, and we've seen how the West behaved towards Japan despite how much Japan wants to be treated as equal. The West never treated Japan as equal back then, and it's pathetic if we Chinese thought we can just wait for others to agree with us and let us in; the West are very hypocritical and only point faults in others and not themselves. Also having them led the world for 200 years, it's about our time to lead as we slowly come to same height. For the same information, it's better for Japan to stop associating with the West so much because "being joining that group of friends",aka bandwagoning in IR jargon, does Japan no good and harms Japan more in the long run. An example will be deployment to Iraq, which led to Japanese nationals dying in Iraq, which could've been prevented. Regardless, I believe Japan will not walk that road again, and was only lost that time, so it was an exception. Other than that, Japan and China respected each other's cultures and learned from each other, gotten along fine these thousands of years, so I believe neither one will threaten one another, nor invade each other, and if we can get through the small differences now, it will be a better tomorrow, and we can be great friends, neighbors, allies, and even brothers. I seriously don't understand why we grew up alongside each other all these centuries without problem and now we need to be sworn enemies. It doesn't make sense, I refuse to believe in it, and I'm a firm believer of Asian integration. I also think it's about bloody ******* time we Asians stop fighting amongst ourselves and cooperate and work together. We are relatives, and that we are armed with modernized societies, technology, manpower, and knowledge, we should actually advance agendas for the protection and the better welfare of our people, not destroy ourselves and each others'. C,J,K can be the leaders to the future, not always letting the West walk on top.
4. This is a lie. If you look at how much China is being accused of being "assertive", this is a vivid example of the West disagreeing with China for not submitting to their wills. China does not speak against them because there's no need to; actions prove the best. Plus, if they aren't intervening with our affairs, there's no reason to talk about them. Another thing is China is mostly focused in internal issues and prefers non-interventionist foreign policies, so it doesn't need to go telling others what to do. To intervene is also not how Asian cultures are.
I really suggest people to learn more about China; it's helpful.
5. crap.
6. I think he's referring to how the Manchus invaded Ming and took over. One must understand that Ming was in full decline by 1600, and another thing was that one of the commanders, WuSangGui, was a traitor and opened the gates for the Manchus to enter. Also the invasion didn't happen in one day, but over a lengthy time span.
Sorry for the incoherence and poor grammar. I'm already very tired after responding to so many posts with all long ones. I want to say everything I've said were things I've studied, researched from many areas, and therefore not some rhetoric without backed claims. I do have good faith in Japan and see the Japanese people as my friends, and want to see the best for all of us.