Re. the illegitimacy, Carol's marriage transcript records Mary as a spinster, so she can't have had a previous marriage if this was correct.
She looks like Mary GELMIR bapt 27 Jan 1822 Kirk German, daur of Daniel GELMIR & Isabella SHIMIN [IGI].
Daniel, Isabella & family are easily tracked through several censuses, but I can't find Robert's father Robert Spruston/Sprooston, who may not have been from the IoM.
Sue