No worries at all Margaret....I love doing this sort of research, though it can feel like I'm going down a rabbit hole at times!
I'm sure your research will help someone along the line.....Sutherlands and Gunns are thick on the ground in these parts, you are bound to match with someone's line sooner or later

None of the couples further back in your line seem to match my family yet....but all the 'frustrated Sutherlands' on this thread are probably related if you go far enough back

Oh, and I can't help myself.....I looked into the other informant on the death certificates
It seems that the G Cormack, informant and son-in-law of Alexander Sutherland was George Cormack.
George Cormack married Jamesina Sutherland in 1887 in Latheron.
Scotland's People reference:
JAMESINA SUTHERLAND
GEORGE CORMACK
1887
038/ 20
Latheron
Be warned though, there appear to be 2 George Cormack/Jamesina Sutherland combinations in the area at that time. The other couple married in Wick in 1896, but they both show in the Latheron 1901 census return!
In 1891 Jamesina appears to be living with her aunts (her mother Jane Sutherland's sisters), which is great as it also gives you Mary's married name.
1891 census - Torbeg, Dunbeath Estate, Latheron, Caithness
Margaret Sutherland Head 63yrs Crofter b. Latheron, Caithness
Mary Finlayson Sister 49yrs General Servant (domestic) b. Latheron, Caithness
George Cormack Lodger 31yrs Agricultural Labourer b. Latheron, Caithness
Jamesina Cormack Niece 25yrs Agricultural Labourer's wife b. Latheron, Caithness
Jane Cormack Niece 2yrs b. Latheron, Caithness
Margaret Cormack Niece 8mths b. Latheron, Caithness
1901 census - Cong?, Latheron, Caithness
George Cormack Head 41yrs General Labourer b. Latheron, Caithness
Jamesina Cormack Wife 36yrs Labourer's Wife b. Latheron, Caithness
Jane Sutherland Cormack Dau 12yrs Scholar b. Latheron, Caithness
Maggie Cormack Dau 10yrs Scholar b. Latheron, Caithness
Hughina Cormack Dau 8yrs Scholar b. Latheron, Caithness
Alex David Cormack Son 5yrs Scholar b. Latheron, Caithness
Janet Dachar Cormack Dau 3yrs Scholar b. Latheron, Caithness
Good luck with sorting out your web....
Jenny