I know two TAs and a librarian who work in a school who are ex teachers.
I would have thought a special school would love someone like him. I suggest he visits the school prior to interview. It would give him a chance to see what the school is like and talk informally to the people he would be working with.
He need to look at the job spec and focus on how he fits their job spec. He needs to focus on his positives. He has worked with people with learning difficulties and has some idea what he is letting himself in for. What sort of special school is it?
It is likely he will be asked on why he is applying for a TA job and not a teaching job. He may well be asked why he gave up teaching.
He says that he hated doing a 60 hour week sounds better than saying he had a nervous breakdown. Teachers know that NQTs have an awful workload. It would be a mistake to say anything negative about the school he worked for.
The LSAs I know who are teachers are working as LSAs for a better family life/ work life balance. He can say that he has small children and he does not want to work 60 hours a week like a qualified teacher does. If women take lowly paid jobs for work/life balance reasons then why can't men?
If I was him, I would mention mental health difficulties unless he is directly asked. Obviously you can't lie on job application forms, but its silly to volenteer information that might damage your chances.