When he received his check from the CSA at his exchange, he signed with an X mark. But I don't think he was illiterate, I think he couldn't see well enough to write. By 1880, he was married, had several children, and was the Supervisor of the Halifax Poor Farm. He eventually had 12 children by his first wife; after her death he had four more by the second wife. Pretty good for a blind guy!
I believe his family considered him to be blind although he may have had some vision. I have looked at census records and have not seen a checkmark indicating his blindness on those that carry that information. However, a photo of him probably taken shortly after he returned home is taken almost in profile which is pretty unusual. His eyes are open but only the left side of his face is visible––maybe he was somewhat disfigured.
I was pleased to see that his story has been told elsewhere and I hope this will be of interest to you.