I have the info you need on Richard Addis. His family moved to Arkaquah, Union Co., GA, before 1850, from SC. Then they moved to Hiawassee, Towns Co., GA, by 1860.
Richard and brother James moved to Tallulah, Rabun, GA, just before the 1880 Census. They lived next door, and seem to have married sisters, Martha J. ("Mary"), and Arminda, respectively. [I say they are possible sisters, because of the way they answered the Census: particularly, neither of them knew where their parents were born. That is a rare thing to leave that blank. And here they are, living next door, married to brothers. They are probably sisters!]
This has led some people to think the Addises came from Rabun Co., when actually they ended up there. Some stayed in Towns Co.
But then again, Rabun Co. is closer to SC than is Union Co., and the Addises could have passed through there, but nevertheless the 1850 Census shows them in Union. It is easy to move from Union to Towns, than from Towns to Rabun, as the former two are adjoined by a low pass. In fact, Towns was formed from a big part of Union (and a little part of Rabun,) in 1856. But to move from Union to Towns was a big deal, because of the high and winding mountain pass you'd have to cross over, just to go view the place!
Moreover, the Tallulah area of Rabun is a good ways from the route to Towns Co. But I am not familiar with Addis Gap you mentioned ... where is it? That sounds intriguing. So, some of them settled elsewhere, besides Tallulah?
Richard's and James' father was William, and their mother was Nancy, both born about 1820 in SC. (The Census changes their actual age every time, but 1820 seems the most accurate.) I did not find a William Addis on the 1840 Census, under any spelling variation. This may have been because he was working on someone else's farm in 1840 (as he was in 1850), and in 1840 only the heads of households were listed, as you know.
Thanks for the information that Martha ("Mary") was a Wooten. I've been searching for that, and now you've saved the day!
I have much more info on these people, and you may see my entire gedcom at the following link: