There are two Hector Sutherlands in north-west Sutherland in 1841.
One, age given as 35, in Achnahuaigh with wife Margaret and several children. Adults' ages in 1841 were supposed to be rounded down to the nearest 5 years, so he would have been born in 1801/1806. Number 1 is still in Durness in 1851, 1861, 1881 and 1891, described as a grocer, born in Durness, with wife Margaret and several children. It looks as if he died in Durness in 1891 aged 85, mother's maiden surname Morrison.
The second, age given as 30, in the household of James Campbell and Jane Sutherland, so he was born 1806/1811. He is described as a pensioner, which at that time meant that he was retired from the army, so I think you can be pretty sure that he is the on with the military service record.