jcarolan,
The surname McNeill is fairly common around the Ballycastle area. Most are descended from Scots who came over from Gigha and Kintyre. A good background read is: “Family names in the Glens of Antrim” by Brian S Turner. Plenty on McNeill, O’Neill, McAllister (another Scottish name) and Murray.
Writing about the McNeills, Turner says: ”For various reasons members of these southern Argyll families made their way to the Antrim coast. They may have come as fighters, farmers, fishermen or migratory harvest labourers. There are 11 recorded in the 1669 Hearth Money Roll, in four parishes – Culfeightrin 5, Ramoan 2, Ardclinis 1 and Tickmacrevan 3. This dispersal of settlement is similar to the McKays, and map 24 shows the modern distribution of these 2 families in the Glens is very similar.” (Turner page 116.)
So that information tells you that in 1669 there were 11 McNeill households in the area where your own ancestor apparently lived.
Your problem is that these parishes really don’t have records for the years you need. Ramoan start in 1838, Culfeightrin 1825, Ardclinis & Tickmacrevan have no records before 1872. So tracing the family will be difficult.
Bill McAfee’s site has the 1803 agricultural census, so you can see where McNeill families were living then, but there’s no direct way of saying which is yours. http://billmacafee.com
Family Tree DNA reportedly has more people with Ulster roots than any other company. That obviously increases the chances of finding a match. You might want to try them or, if you have already tested, you can transfer your results to them for no fee.
The North of Ireland Family History Society is running an Ulster DNA project in conjunction with FTDNA and can offer testing kits at a reduced price. http://www.nifhs.org (Go to DNA project on the website).