With regard to finding any siblings for Minnie, as I mentioned previously your best bet is to go to PRONI and search the Killyman Church of Ireland baptism records between 1853 and 1863. Those records are not on-line anywhere so far as I can tell.
You might expect there to be more children than the 4 you have found but it wasn’t uncommon for children to die young and so it’s possible that the only ones to make it to adulthood are those you have already found.
The Killyman parish records also contain burials up to 1875 so you could check them too. A personal trip to PRONI is required or you could hire a local researcher.
With regards to locating the McFarland farm, it seems pretty likely the farmhouse was plot 23aa which as I mentioned before is on Bovean Way, not too far from Moy. There is a loop road called Bovean Rd that runs from Bovean Way in a rough rectangle. The farm was at the side of the road on Bovean Way between the two arms of Bovean Rd. You can see it on Griffiths Maps (use the slider bar in the top right hand corner of the screen to switch between the contemporary map and a modern one. There is also a satellite view which shows that the property has long been demolished.
I have attached a copy of the revision records for the townland c 1930 taken from the PRONI website It shows that plots 23 & 24 were farmed jointly by John Irwin and Nammy Armstrong. Armstrong also had other land in plots 23 and 25. Altogether over 38 acres. The Irwin property was only 1 rood (a quarter of an acre). Yet his probate file says he was a farmer. So my guess is that he was farming the Armstrong land as well. That land is all still working farmland today but as I say the Irwin/McFarland property is long gone.
The land is shown as “in fee” in 1930 which indicates they had bought the freehold. (Normally done via a Government arranged mortgage under the 1903 Land Act).
In the 1911 census there were 24 households in Bovean and a total population of 90.
http://www.census.nationalarchives.ie/pages/1911/Tyrone/Drumaspil/Bovean/
You could try calling at any of the farmhouses around that area to see if anyone knowns of the Mcfarland family. I did search a newspaper site for any mention of them in Bovean but without success.