Ref your reply 7. There are numerous posts on Rootschat where children are registered in the man’s surname but the couple never married.
In doing so - one of 2 things can happen on the birth cert
The mother is shown as Susan Gadney nee Wells - giving the impression the couple are married
The mother is shown as Susan Wells
Do you have a copy of either of the first 2 children's birth certs?
Logic dictates that if they were married - why would she be referred to as Wells in relation to the assault charge in 1840?