According to my guide to Church of Ireland records, the early Castlemore records were destroyed in the 1922 fire in Dublin. (Ironically they had been sent there to the Public Record Office for safe keeping). About 40% of all early COI records were lost in that fire. All the RCB library has are baptisms from 1890 and marriages from 1847 (which are on-line anyway).
Your book extract says that Parson Little Morrison was buried in the Old Cemetery in Ballaghaderreen. So perhaps there was a family plot there, and that might be where Margaret was also buried.
Griffiths Valuation for 1856 lists the Rev Anthony Thomas as occupying the Glebe property (plot 1 in the townland - Ranagissaun, in Griffiths). At that time it was 44 acres of land, a house, offices (ie outbuildings) and 2 cottages. Later changes to Griffiths records are noted in the Valuation Revision records, in the Valuation Office in Dublin. Those records are not on-line at present but should show any additional properties on the plot, and changes of occupant.