Your son might really enjoy programming language theory and construction. There's a lot of active research into programming languages, and even full-time jobs creating new programming languages!
One of my first jobs out-of-college involved making a small language for loan origination. And a few years ago, I got an offer to design a language for a quantum computing company!
Even if your son doesn't get a job designing languages, programming really scratches the reading/writing/lexical itch. I suspect that he would be a very happy developer :)
If you have any questions about learning programming or career stuff, feel free to email me at hello@taylor.town or schedule a 30-minute chat.
[1] https://taylor.town/tpbsl-guide
[2] email: hello@taylor.town