Well, to answer the first point, greater economic ties and investments and a common fear of Chinese interests normalized Japanese-Filipino relations. Granted, their relations mainly soured during the war and the two aren't geographically close and thus lack some of the conflicting interests of Japan-rest of East Asia, but it'd be a start. Geopolitical goals and economic ties trump past ties, as mentioned above with the examples of US-German and US-Japanese relations.
On the other hand,
And make it happen to the domestic audience of Eastern Asian leadership who has no memory of war and all those atrocities, while real, are just ancient history.
WWII has been a while but it's hardly ancient history and, while the survivors are certainly in dwindling supply, there were plenty of people who lived through WWII or were raised by people in the 70s-90s and that sort of political climate is hard to dissipate without a great deal of effort towards reconciliation by both sides, which, as you've noted, is not the case at the present.
And it's not just an issue of Japan's neighbors; Japan's own revisionist actions with their history textbooks, for example, have only succeeded in enflaming the issue. The Yasukuni Shrine visits by various politicians as well, while private ventures, are an open source of agitation as well and have been for decades, yet Prime Ministers like Shinzo Abe, knowing full well what reactions their visits would incur in their neighbors, have time and time again gone to the Shrine.
Japan's territorial disputes with its neighbors makes it much harder for anti-Japanese sentiment to die down, besides. The Liancourt Rocks dispute over the rich seas in the Sea of Japan/East Sea and the Pinnacle Islands in the East China Sea make it much easier to keep a grudge against Japan alive, since the justifications for those issue are somewhat rooted Japan's colonial past (when exactly they acquired them and by what legal means, as ownership there was fuzzy until the 1890-early 1900s when Japan was the sole formal owner) and thus tend to get tied up with other unresolved issues between Japan and its neighbors.
And Japan's poor relations with the rest of East Asia isn't just a WWII thing; Japan chipped away (and later tore) various parts of Chinese land from the Qing and Republic of China over the course of 50 years (from the First Sino-Japanese War to WWII, 1890s to 1940s) through multiple wars and diplomatic incidents, with most of them being started by Japan and overtly aggressive in nature (the Mukden and Shanghai Incidents were staged by the Japanese military). Korea had been colonised by Japan for around 40 years, having lost its independence right when it had begun active modernisation efforts and thus was forced into Japan's militaristic ventures (which ultimately led to the partition of the peninsula).
And it's not like Germany's exempt from the snide comments and strained relations with its neighbors, with Jarosław Kaczyński proving as much. Making references to Japan's atrocities become laughable isn't happening if Germany still gets criticised for its past crimes and Japan isn't willing to go as far as Germany to try and smooth over relations with their victims.