Technically, Buddism isn't a non-exclusive religion. Unlike many religions, you can be a Buddist and a member of another faith and still be considered a good Buddist.
Not really. Historically, only the particular Japanese form of Zen (Chan in China and Son in Korea) accepted that one might be 'Buddhist' (actually meaning a Zen meditator; not the same thing really) and be something else as well. In the Vietnamese Zen tradition in which I was originally ordained (Liu Quan Thien) they'd tell you you're going to Buddhist hell as quickly as any fundamentalist Christian. Same goes for the orthodox Theravadins and Tibetans. The confusion arises because 'Buddhism' as practiced by white folks here in the west tends to be more a New Agey, inclusive, feel-good, yuppie trip, as opposed to anything resembling the true teachings (of ANY school). This is good in some ways ... bad in others. And of course, this varies among different centers.
More definitively, Buddhists look to find the virtue in all types of philosophies. Enlightenment comes from accepting what one believes to be right, not what one is necessarilty told to be right. Yes, many Japanese are Buddhists.
Point 1 ... see previous paragraph.
Point 2 ... Not even close.
Point 3 ... The Buddhism practiced by the majority of Japanese officers during WWII was a mish-mash of Rinzai Zen (very militant), Shinto, and anscestor/Emporer worship. And yes ... many Japanese Zen monks/teachers supported the war because they were human, like the rest of us, and got WAY off track in the nationalistic fervor of the times.
BTW ... The Japanese are among the most racially predjudiced people on the earth. Ask anyone who's lived among them. And consider the Sri Lankans and the Tamil issue. Trust me ... Buddhists don't have a lock on wise, compassion, treatment of their fellow man. They can be just as militant as any other group. Well ... not as dicked up as the Christians and Muslims, of course ... but you know what I mean.
Reverend Thich Minh Thong