The marriages for Magheraculmany in 1861 are on-line. Just for some reason 1861 isn’t offered on the year menu. I looked through them. I found a marriage for Terence McNulty to Ellen Breen on 30.12.1861. Witnesses: John & (?) Alice McWade. It’s the last marriage in 1861. See:
http://registers.nli.ie/registers/vtls000632829#page/100/mode/1up
So that tells you that the bride at least probably came from that parish. The Magherculmany RC baptism records start in 1836 and marriages in 1837.
I looked at the Magheraculmany baptisms which start in 1836 but did not see Ellen’s baptism. The records for that period only give the child’s name and the father’s name. No other information. So no mother or townland etc. The early records are hard to read and some are damaged. So can’t say for certain she’s not there. You might want to look yourself. The parents’ marriage would be before the records start.
The reference you have found in Griffiths tells you that a Philip Green was farming in Glenarn townland in 1864. He had plot 28 which comprised 30 acres) roods and 35 perches. (40 perches in a rood, 4 roods in an acre). So just over 28 acres. The financial information tells you the value of the land (for local taxation purposes). That type of valuation is still used to this day to assess local property taxes.
Griffiths lists heads of household who have property of a value worth taxing. It’s not as comprehensive as a census. There are plenty of people who aren’t listed eg servants, lodgers, people with houses of too low a value to be worth listing etc. However if you know from a marriage or death cert that your Philip was a farmer then you would expect him to be listed. And if this is the only Philip in Magheraculmoney parish, then that increases the chances you have the right family. (Your Philip might have died before Griffiths was compiled and so not be listed).
You can use the revaluation records to take the Griffiths records forward. Using those records I see that Philip was replaced as tenant by James Breen in 1865 (suggesting that Philip may have died). James in turn was replaced by James junior in 1903 and he was replaced by Catherine McCann in 1925. That series of records stops in 1925, though there are later records in PRONI, Belfast which take the information forward to the 1960s.
http://www.proni.gov.uk/index/search_the_archives/val12b.htm
There were 4 Breen households in Glenarn in the 1901 census. 2 of them contained a James so a bit more work would be required to find the right one:
http://www.census.nationalarchives.ie/pages/1901/Fermanagh/Lack/Glenarn/
I think yours is probably house 5 in 1901 because there’s a James senior and junior plus a daughter Catherine who is probably the Catherine McCann who inherited in 1925.
3 households there in 1911:
http://www.census.nationalarchives.ie/pages/1911/Fermanagh/Lack/Glenarn/
One is Church of Ireland, 2 RC. They may all be related though. (Someone has switched denomination over the years).
http://www.census.nationalarchives.ie/pages/1911/Fermanagh/Lack/Glenarn/
Going backwards, there were 6 Breen farms listed in Glenarn in the tithe applotment records for 1826, including Philip Breen:
http://www.ulsterancestry.com/ShowFreePage.php?id=415
I searched for a death for Philip Breen 1864 – 1868 but did not find one. That suggests he probably died pre 1.1.1864 when statutory death registration began. Griffiths clerks dates were often out by a year or two so the change of tenant in 1865 isn’t out of place.
I looked for wills for Breens from Glenarn but did not find any.