Looking through soldiers' records, there's a possible circumstantial fit with a William Adams, labourer, born Killead, Antrim circa 1854. he joined the army in 1876 in Belfast and was transferred to the Reserve in 1888. He was discharged in 1892.
Father Robert, mother Margaret.
Belfast addresses in the 1888-92 period were 17 Belmont Street and 13 Lagan Village.
He served In Lucknow in 1878 and 1879.
No mention of a marriage.