Was Mary married to Isaac Debnam when she was Mrs Debnam, because, if so, she married with a name other than Conyers, if you look at free BMD. So either she married him as a widow too or she and her father shared separate surnames.
Also, if you have the Debnam marriage cert maybe that will have Scotter on with a different first name and will tell us if he was dead or alive at the time of that marriage.
Like Scots may be called "Jock" perhaps Scotter was called scotter because he came from Scotter in Lincs rather than it being his baptised Christian name. My father was edwin John but everybody called him Jack.
Fizzy