I am not sure about the hormone therapy questions - I suspect it would depend a *lot* on when and where he was, and also exactly what doctors he was going to - but I think it's very unlikely even today that any doctor would look at a child with unambiguous male gentalia and no obvious dysphoria and say they were "actually female" regardless of their genes or hormones, doctors tend to go with genitals if asked to make a call. If their genitals are in some way ambiguous, with CAH they would likely have been tagged as intersex at birth, and decisions about how to socialize them would have been made with the parents then (and possibly revisited later). In my understanding of CAH, XX people with CAH are very unlikely to have unambiguous male genitals anyway.

I'd advise you to tread carefully regardless if you want to go in that direction; the question of treating children with hormones is a *really* hot-button issue politically right now in many countries and you could end up telling a story that was harmful to real-life people dealing with serious threats if you weren't very, very careful.

Anyway, if all you need is a dude who is intersex, has complicated gender feelings about it, and has bodacious bosoms, I would probably go with Klinefelter's syndrome. Most people with Klinefelter's are raised cis male and many are not aware of their condition until puberty or later if at all, and breast development (gynecomastia) is a common symptom. (Although if you don't need him to have a lifelong intersex condition, gynecomastia happens in cis males not infrequently too, due to a variety of things. And many heavyweight men develop nice boobs without any medical condition.)