I searched the Irish Family History Foundation's database. It has nearly all surviving Irish rcds except for 13 Cntys. The database has 11,500,000 rcds. Rcds B4 1840 are sparse. Many B/M/D events were never rcd'd, or haven't survived.
The Saddler surname is not too common in Ireland. The earliest birth/marriage rcd for the surname Saddler (+variants) in Leitrim is a M in 1821. The earliest birth/marriage rcd for the Saddler surname in Ireland is a M in 1741.
To match an early Armstrong marriage with a corresponding Saddler marriage in the same county, the same year, and the same parish in Ireland is daunting. Your chances are very slim given the state of early rcds.