I am also pleasantly surprised to find someone else interested in the Haven family.My niece Angie is currently working on this genealogy, and the information which you provided agrees with the information which she has given me on Thomas and Elizabeth Haven and on Martha Ann and John S. Haven. Angie's records show Elizabeth (Betsy) Johnson's father as Jonas Johnson?She has been unable to find information on Jimima Johnson's mother.
We are unsure about the family name of Abigail Blackshear Welch.She has found it in some records as Gill and in other's as Blackshear. I have heard, but cannot confirm that Abigail Welch's grave is at the cemetery of the Methodist Church in Reno, Georgia.
Richard White who is a descendent of Mary Ann Haven has a web site which has some information concerning the Haven family. The site is http://pone.com/ts/rw000.htmhttp://pone.com/ts/rw000.htm
The Florida archives in Tallahassee has some pictures of Martha Ann and John Shephard Haven in their historical photograph collection.
Angie is currently trying to find Richard Welch's parents.According to family lore they could have been Cherokee.Will share with you if we find anything.