Rathcoole Hill appears to be a local placename as there's no mention of that I could see on the historic OSI maps, but Modern OpenStreet maps and Google maps show Rathcoole Hill Road to the south west of the town which is probably where it was located. The other end of the road is named Stoney Hill Road and heads north east to Rathcoole. Rathcoole is about 115 m above sea level, and there are parts of Rathcoole Hill / Stoney Hill road are over 180 m, with areas to the east of the road over 300 m, so a gentle hill. Most of Rathcoole Hill road is in Redgap townland, which borders several other townlands - i.e. : Glebe, Carrigeen, Crockshane, Rathcoole all in Rathcoole civil parish, and also Coolmine townland in the adjacent civil parish of Saggart.
The nearest Library is the County Library in Tallaght , see link to the FamilyHistory section at this link, in addition to resources held at the Library they also have some online, e.g. South Dublin Images and a map tool with a selection of historic layers dating back to 1760. The library also hold some Graveyard Inscript publication, bear in mind that not everyone could afford a headstone.
I'm not aware of any additional Graveyards in Rathcoole or Saggart - the Dublin Graveyard Directory only shows these along with a much later graveyard in Newcastle, which was part of the same Catholic Parish as Rathcoole & Saggart.
The library also hold directories, but based on the civil births I looked at James was noted as a labourer so probably would not be listed - I'll check in the copies I have. School records, if these survive, would probably end up in the National Archives (Bishop Street, Dublin City), but would double checking in Tallaght in case they have any details.
I believe that Hallowed is probably a local spelling variation for Hollywood, it's mentioned by John Grenham in his surname dictionary as a rare variation of the surname Hollywood . There are several townlands in Co. Dublin and Co. Wicklow named Hollywood, along with a number of houses/estates.
Did James and Elizbeth stay in Co. Dublin - have you located their death records ?