Revernd Galbraith Richardson - Descendants

Good evening,

I'm searching for the birth/marriage/death records of this gentleman & his descendants in Ireland. I believe he was my 5X Great grandfather. 

He may have been the celebrant for his son Henry's marriage (wife unknown) Brn abt 1758. Family heresay says this Henry was Proctor of the Irish Admiralty. His son, William, was born in Corakagh, South Dublin abt 1815, migrated to Australia (Van Dieman's Land in 1841).  

I am searching for any records that might inform of the BDM of his descandants.

Here's what I have collected on Galbraith so far:  

Leslie’s “Clergy & Parishes, Clogher” Pub. 1929.
This book is at the Church of Ireland Cathedral in Clogher, County Tyrone, Ireland. 1741 Galbraith Richardson (V B). See Leslie’s Armagh p.299 (NB: another book written by Leslie, mentions Galbraith).

In 1738 Galbraith was Licensed Curates Assistant. From A Topographical Dictionary of Ireland, 1837 TERMONMAGUIRK, or TARMON-McGUIRK, a parish, partly in the barony of STRABANE, but chiefly in that of OMAGH, county of TYRONE, and province of ULSTER.

In 1743 he was Rector of (Armagh) Errigal Keerogue. He was presented by James Richardson, his elder brother. James who later became James Mervyn. Source: Diocesan Registers, containing records of institutions, consecrations, ordinations etc
 

His P.Will dated 2 June, 1778 was or. in 28 Jan. 1780 mentions his wife Catherine, and his 3 sons, Captain William, Henry (ent. T.C.D. Jan 19, 1774) aged 16, ed by Dr. Grueber, b. in Co. Tyrone B.A. 1777 M.A. 1781) and James and 4 daug. Jane, Dorothea, Catherine & Eliza. (wife of Sir Wm Richardson (Bart).)

Please excuse my ignorance of the geography there. Name changes and various spellings make it difficult to determine if I'm chasing the right lead. 

Any information would be very much appreciated.  If I should be hunting in other Parishes - could you please advise.

Many thanks.

Kind regards,
Racheal.

(Richardson)