Heather,
I cannot answer your name change question but I had a look at a couple of sources.
Flax Growers Register 1796 John Dunbarr (sic) parish of Clogher, Tyrone
Griffiths Valuation 1860 William Dunbar rented a House, offices (Barns etc) and six acres if land in the townland of Ballaghneed, parish of Clogher.
Regards