You don?t say what denomination Ralph was. Looking at the 1901 census for Co. Donegal, there were 140 people of that name in the county. The vast majority were Church of Ireland, though there were a few RC and some Presbyterian.
The Church of Ireland baptism records for the parish of Killaghtee start in 1810. RC in 1845. I don?t know which would be the nearest Presbyterian church, but I doubt it has records for the 1790s. Few do.
I looked in Griffiths Valuation for 1857. There were two Maxwell households in the parish at that time. A John M was living in Killultan where he had a house and small garden. William was in Ballyloughan where he had a house. (Typically agricultural labourers cottages).
You can see a picture of the church and a list of graveyard inscriptions for Killaghtee Church of Ireland on this link. There are no Maxwells listed but that doesn?t mean they are not there. Simply that, like the majority of the population, they couldn?t afford a gravestone.
There?s a John Maxwell listed in Killaghtee in the Hearth Money records for 1665.
There?s also a Robert Maxwell listed in the Muster Rolls for the area in 1630 or thereabouts. He was on the land of the Earl of Annandale which perhaps gives a hint as to where the family may have originated in Scotland (The first Earl of Annandale, John Murray, came from Wigtownshire). The original Planation settlers often brought tenants from the Scottish and English estates with them.