The first two records (1.) in your document, the deaths of Patrick McCabe in 1877 and Anne McCabe in 1896 are civil death records, so the Castletown reference in these is to the Civil Registration sub-district of Castletown, which was part of the overall registration district of Navan. This sub-district covered areas north of the town of Navan including parts of the following civil parishes - Castletown, Drakestown, Kilshine, Knock, Donaghpatrick, Clongill, Kilberry, Rathkenny, Gernonstown and Stackallen. Ladyrath is in Rathkenny civil parish is included as one of the townlands covered, but no sign of a townland named Gravelmount, Gravelstown townland, which I mentioned in the earlier reply is in Emlagh civil parish and quite close to this district, but officially covered by Kells registration district. There are a number of possibilities - the Gravelmount mentioned on Patrick's death is a local place-name so not an official townland name, or or his death happened in Gravelmount in Emlagh, but it was registered in Navan district by mistake - maybe he died away from his place of residence ? I checked the area on the historic maps and see no mention of a Gravelmount...suspect the reference is probably a variation for the nearby townland of Gravelstown.
In case the location is indeed Gravelstown, Emlagh then the distance from this townland to Ladyrath, Rathkenny townland is about 10km (~6 miles) east of Gravelstown - see Google Map, the village of Castletown is less than 5km (~3 miles) north west of Ladyrath.
2. The baptisms took place in the Catholic Parish of Castletown/Castletown-Kilpatrick, which although having the same name, covers a different area compared to the registration sub-district, or the civil parish of the same name, so at the times these children were baptised the family could have lived anywhere within the parish, which at the times covered the five civil parishes mentioned earlier - i.e. Castletown, Clongill, Drakestown, Kilshine and Knock, about 28 townlands in all - see attached document below "Castletown-Kilpatrick-RC-townlands" for a full list (Catholic parish boundaries were not always as well defined as Civil districts).
3. Kilshine civil parish is included in Griffith's Primary Valuation, select the search by place-name option and Co. Meath as county and enter Kilshine as the search - the four townlands for Kilshine are listed. The village and Catholic parish of Castletown are often listed as just Castletown, and that's what is listed as on Griffith's Primary Valuation, to search for townlands in this civil parish select the search by place-name, Co. Meath as county and Morgallion as Barony (to filter out other Castletowns...) and Castletown as the placename - the townlands for Castletown (Kilpatrick) as shown.
4. As mentioned above, Ladyrath townland is in Rathkenny civil parish so that Griffith's record for James McCabe is the same location as that given on Anne's death.. The Grange reference appears to be a record from the Tithe Applotment books is in Kilshine civil parish (recorded as Kilsinea in the Tithes) - one of the civil parishes within the Catholic Parish of Castletown, Co. Meath. This Grange townland is located very close to the village of Castletown - abt. 2km west of the village.