Elspet Grant dau of John Grant and Elspet Hay christened 06 JAN 1801 Inveravon, Banff, Scotland. Looks right to me and follows the Scottish naming custom in her children.
Alexander Stewart marriage was not in Cullen in 1830 according to SP, it was 15 Nov 1831 at Inveravon, Banff.
Which is looking even better for the above Elspet Grant to be his spouse. Marriages normally took place in the brides parish, though banns were called in both the grooms and brides parish if CofS.
Following the Scottish naming customs Elspet/Alexander would have a first daughter Elspet (I note Elcy reverts to Elspet after her mothers death on 1851 census) and second son John.
As that is so then it looks likely that Alexander's father was also Alexander as this is what he names his first son.