Are his parents originally from East Asia? What part? The Philippines is different from Vietnam, and Vietnam is different from China,
East Asians in the US in general have a culture where doing really well/ achieving material success is very important (I'm in the US and have many E Asian friends or ethnically E Asian having been born in the US. The Tiger Mother phenomenon is real, at least among Chinese families. Philippinos are more laid back). Knowing your baseball and having a favorite football team and eating an American diet doesn't mean your family culture isn't Polish or Irish or Chinese or Indian, or that you won't be greatly influenced by it.
It would be pretty much unthinkable for him to be openly gay in many families of East Asian origin in the US, especially if the parents were from the country of origin because family image is very important. Marrying and having kids would be expected as well as having a career, preferably a professional career, and preferably a wife from the same ethnic background or the same profession if not. Marrying a woman from a different ethnicity who worked as a hospital cleaner would be a huge no-no. Marrying a fellow dentist/ lawyer/ doctor would be acceptable.
Why did he leave the US?
The details he's told you about his family might not be quite accurate. He might have absorbed the impulse to present a 'normal, well-adjusted family' to the world. You have no way of checking his account of family life.
He is hiding simple things from you and avoids certain topics of conversation - Why?
Is he used to hiding certain aspects of his life from family members, perhaps a mother, perhaps a father? Is secretiveness a reflex for him?
Above all, his history of short relationships rings loud bells. He is either lying to you and believes a history of short, failed relationships with women sounds better than a porn addiction or fundamental attraction to men, or he keeps on trying but failing with women because of a sense of obligation he has (he clearly doesn't have the toolbox necessary to keep a relationship going, so obligation is the only other motivation he could have).