Hi Daryl,
You may already have this, but this is probably Helen and daughter Carr in 1851. They were both using their maiden names! Looks like Andrew was already gone by then, although I can't tell from the Ancestry transcription whether or not Helen is a widow.
1851
8 India Street, Montrose, Angus
Carr Bruce, 29, Head, born Logie Pert, Forfarshire, Seaman's Wife
Helen Mitchell, 61, Mother, born Logie Pert, Forfarshire
In 1841 Helen is with two of her sons. Alas, Andrew isn't there. I assume I'm just repeating your vain efforts, but it will help for others to know what has been done.
1841
Hill Craigo, Logie Pert, Angus
Hellen Bruce, 50, born Angus, Ind
David Bruce, 25, born Angus, Ag Lab
James Bruce, 20, born Angus, Ag lab
Jean Robert, 9, born Angus, F S
I'm just going by the names of the children as given in a parent search on the IGI.
Have you tried to trace any of them down to see if the name and profession of their father agrees with Helen's death cert? Probably does, and it won't change the fact that he is not with the family for a single census

But a name like Carr is so remarkably different that it seems to be begging to be followed through the years
All the best,
Sarah