“The key may well be in getting the right teachers who can understand him and provide encouragement.”
I think in IEPs, the head of the student services program or whatever it’s called tries to find teachers that would best fit the student’s style.
“Three years, preferably four, of a foreign language are now required for UW-Madison.”
https://languages.wisc.edu/policy/
That depends on the college, engineering ,education, e.g. do not have requirements. You can also get out of the requirement with a documented disability.
“Does Latin always count as a foreign language for college graduation requirements?”
It should, not sure if you’re specifically asking about Wisconsin, but given they have a Latin dept, Latin should count. There’s also an AP test for it so you should be ok. The only issue would be if you went to a college where the AP test couldn’t fulfill the language requirement and Latin wasn’t offered, so your son would have to start from scratch in another language.