I am not sure why you think there is a doubt about the right Stephen Christian. Is it the Sage connection that bothers you?
Stephen Alfred Christian and Sophia married in Chorlton Lancashire.
In 1881 Stephen Alfred (b. Douglas aged 22) is living with Stephen, master tailor (b. IOM aged 47) and Mary Christian dressmaker (b. Market Drayton, Salop aged 45). In the household are some Ralphs
Adam (Mary's bother?) 32 married joiner, b. Market Drayton, Francis 9 b. Liverpool, Louise 8 b. Liverpool, Esther Ann Cohlon 17,
Dressmaker b. IOM.
In 1871 the two Stephens and Mary are in Chorlton.
In 1861 Stephen 28 is a tailor living in Albert Street Douglas with Margt. K Christian 30 dressmaker b. Malew and Stephen son 2 b. Douglas (RG9/4419). Thomas Kelly 80 House Carpenter and Margaret 74, both born Malew are with them.

The IGI only has three Stephens. These two and a third born in Patrick in 1860 who was buried aged 26 in 1886.