Have you contacted Bob Adair whose ancestors came from the Ballynahinch co. Down area. re your will query Perhaps you might start by putting this question to - http://proni.nics.gov.uk/records/wills.htmhttp://proni.nics.gov.uk/records/wills.htm
There has been a book published by the Irish Manuscripts Commission "Registry of Deeds, Dublin, Abstracts of Wills" edited by P. Beryl Eustace, but I am not sure what they hold in Dublin. Perhaps another who may be able to hlep may be:
I think he has on his site - "East Ulster Irish Chronicles. Calendar of Wills. Diocese of Dromore 1678 - 1858"
He may have them for the Diocese of Connor, Down, Dromore, Newry & Mourne, but I am not sure.
My cousin in England looked up "Betham's Abstracts of Armagh Prerogative Wills" which are on microfilm.I think the index to the above "Betham's" is a book by Sir A. Vicars "Index to Prerogative Wills in Ireland 1536-1810 (FH929.342234 C563) which is usually found in City libraries.
I do not know if the Wills which you are seeking would be on these, but the Diocese of Dromore was next to that of Armagh, so it may be probable. If they are, then perhaps the Church of Latter Day Saints may be able to advise and order it in for you. I have a feeling though, that there may have been some problem in finding out which reel they are on, they may be able to advise. Sorry I cannot be of much help.