Hi
He could have done a bunk but women usually still gave their status as married on the census when that was the case as they still were.
The three signatures on the three marriages don't look particularly similar.
The problem with the 1848 death is the age of John on the 1851 census, and if the same child, 1861 and 1871 censuses. There doesn't appear to be a baptism for te child.
Regards
Valda