I am not going to comment (directly) on the Fallon family again until/unless OP returns.
However, I do want to point out that there is an unusual issue with the location of Ballyglass.
Assuming for the moment that this is the Ballyglass townland in the civil parish of Killinvoy, then I find the following:
In the 1827 tythe valuation of Killinvoy, Ballyglass is listed as 167 Irish acres, equivalent to roughly 271 English acres.
But in Griffiths Valuation of 1857, Ballyglass, parish of Killinvoy is only 77 English acres!
And in Townlands.ie there is no listing for a townland of Ballyglass, civil parish of Killinvoy at all!
Turning to the original OS maps, I see the following
Ballyglass, Killinvoy CP, 77-1-15 acres, directly to the north of
Ballyglass, Rahara CP, 300-0-24 acres.
Looking at Griffith's Valuation for Ballyglass, Rahara, I see Malachi Fallon sharing 70 acres equally with John and Michael Mulligan. BUT - none of them have a house, so none of them are living there!
Then, looking back again at the tythe valuations, this time for Rahara, Ballyglass is again listed - exactly the same page as for Killinvoy.
In townlands.ie it turns out that Ballyglass is listed as a single townland of 376-1-15 acres, under Rahara, comprising what was two townlands in Griffiths. The townland is located here:
https://www.townlands.ie/roscommon/athlone/rahara/scregg/ballyglass/