Maybe you should start small. Next time you and your father get into a tangle of code-switching, casually ask him which was harder for him - learning English or learning nuclear engineering..Whichever answer he gives, ask him for an example of the hardest thing about it. With a little luck he’ll provide an anecdote and you can ask about a detail in the story.
It’s like peeling an onion; you’ll have to go through a lot of layers to get to the juicy part.
First, really appreciate the detailed reply. BTW, for context, I learned Mandarin at the University of California, first moved to Taiwan in 1982, and 1985 to mainland China. 22 years in China, HK and Taiwan total since then, Shanghaiese wife, kids all born and years in Shanghai. I’ve lived the progression from Taipei having rice fields in what is now the city center (敦化南路), the morphing of strict Taiwanese vs Mainlanders into a multi-cultural and intermarriage society, and progress from a 3rd world country with great infrastructure and pretty clean air.
Second, where the hell is he from? Like anywhere else in the US or the world, people are different based on where they grew up. And in China, that means the native language one speaks. Ask him 老家在哪里？That is the window into his soul. Seriously. That clue will help you unpack an awful lot of stuff. You might even suggest a Kunta Kinte visit back to the home village. [My experience of visiting my father in law’s tiny ass village in Hubei Province as a) awesome, b) made me fall in love with my Shanghaiese wife all over again, and c) seriously enlightening to his journey.
Third, obviously he’s a mainlander (外生人）but travelled a non-traditional path going from China to the US to Taiwan as a serious professional. He’s proud of swimming with the sharks in America, and it is no small achievement (especially for that day and age).
Fourth, is your mother a native Taiwanese that speaks Taiwanese （闽南话或者客家话或者山地话)? There’s a whole multi-cultural journey that entails.
Feel free to PM me if that might be helpful.
Net net, I would highly encourage learning about where he grew up, the challenges, the journey, and especially call out that you would absolutely LOVE to go to the old country （老家）with him before it’s too late.