Congratulations on truly committing to your children’s education. It takes a level of involvement that most parents might talk about, but won’t commit to. Especially not over a period of 12 years. Well done!
It's not / wasn't easy, but when you see their academic success it's 100% worth it.
1. How did you teach more specialized subjects? I had trigonometry, calculus, chemistry and physics in high school — and it was tough. Especially in math, I didn’t see anything in college that I hadn’t seen in high school until I was more than halfway through the second college calculus. But there’s no way I could have taught any of that stuff when I was of an age to have 16-18 year old kids
We taught them until they pushed our limits. My wife is a grammar ninja and I had two years of calculus in HS, plus more in college. That said, I stopped teaching them math after Algebra II and relied on hired guns (professional tutors) to handle it.
That's what we did in all subjects - handle what we feel like we have a handle on, then fall back on professionals (1:1, not classes) to make sure they received the best education they could.
I'm a firm believer that 1:1 teaching is far better than any situation with multiple kids and one teacher. Our children could rocket through a subject they easily understood then hit the brakes and loiter for as long as needed to completely grasp a subject before moving on. Moving at the 'average speed of the class' is hard on everyone except the average.
2. Also less-quantifiable stuff, like literature? While I loved Catcher in the Rye and even The Scarlet Letter (I was strange that way), I don’t think I could teach either.
Partially via tutoring (there are tons of options in that regard) as well as curriculum (both online and physical). Homeschooling was more difficult 20 years ago but there are tons of options now for parents.
3. How did you handle the social aspects? Working and playing with others, and later, dating. Learning to respect and deal people different from yourself, and learning where to draw the line when “different” crosses over into “not morally right.”
This one is easy - much easier than people tend to assume. Our kids are quite social, well-adapted, not at all the 'typical home school kid' that people tend to picture (socially awkward, etc). In fact, most of the public HS kids I meet are far more awkward than they were.
We didn't home school them to shelter them, we did it to give them the best education possible, so they have rich social lives.