Is the name Calahan/Callaghan and various other spellings or Cahalan ie perhaps spoken Callan/Cullen/Carne or Caalan? You are using it interchangeably.
Could you let us know what the most recent spelling if the name is please.
This website
https://www.irishgenealogy.ie/en/is good to find BDM, also Family Search
ETA I am also getting a little confused about the names and when you are using maiden names and when you are using married names
Is it Bridget Calahan Sharkey born 1818 in Tibohine Co Roscommon
married
John Sharkey when and where?
Bridget ms? born 1840? Ireland
married where and when?

Died when and where??
Michael Calahan born

?? where
died 1871
Margaret Calahan born 1871 Bradford England
married
died
If you could fill the gaps that would be great.
Have you checked later censuses?