The nearest CofI Church to Mecklenburg St (later named Tyrone St then Waterford St/Railway St) that I can locate is St Thomas Church, which was located towards the northern end of Marlborugh St. at the junction with Gregg's lane, and not far from the location of St. Mary's RC pro-Cathedral.
The church was destroyed in 1922 and rebuilt just off the original street on the street now named Cathal Brugha Street.
The directories for that timeframe are very limited in the information they contain (Thom's didn't start publishing until 1844), and only a small number of people were listed, and dont contain a street listing. I have a Treble Almanac/Wilson's directory for 1813 - I'll have a look from Daniel later on. Do you know a trade or profession for him ?
Shane