What he has seems more like a fetish than a disability.
He's fully aware of how to act in public. He'll even put on clothes and mental capacity to go shopping for things he needs. So he has the capacity to act like a fully functional adult in a job where he interacts with the public. He only indulges in baby mode in the privacy of his own home. Sounds a lot like many other's with fetishes. They do not receive government sponsorship for their hobbies and neither should he.
I could care less about what he does in his spare time, he just needs to learn to do it on his dime. Not our's.