Maybe I can help a little. But first I found your comment about Guilford County very interesting as I have some info on the Middletons in that area but had not connected that area with Bute. I had always thought the Bute area came from Granville Co. Now I need to go back to the Guilford records. I do know for sure that "our" Thomas Middleton (probably JR) was in Guilford Co. ca. 1809. I found a document in SC where a man who lived in Guilford died and a son and son-in-law came to Lancaster County, SC to find Thomas and another man named John Hilliard who owed the estate some money that was borrowed in 1809.
I don't think James, John or Daniel ever maried. I have copies of their wills and everythng was left to mother and siblings. Yourith married Thomas Cates (James and Yourith are mentioned on Thomas Cate documents in Orange Co., NC way back in 1760's) Yourith did indeed out live Thomas Cates. His will names her as executor and she is on the 1820 Census for Newberry Co., NC. I have the papers where Thomas is relieved of his duty as executor of James SR's estate. I have a copy of James' Revolutionary War papers (DAR) and it contains a copy of Pleasant Basket's Bible record. So I have that as well. I have not been able to find anything on Yourith's parents prior to her father's will. Have bits and pieces on her siblings. I have more on Thomas Middleton's children. He had a son named James (probably the same James B. Middleton mentioned in Mary Clark's will which also names Malcom Clark Middleton, grandson of Thomas.) I know that Mary Clark only had one sister who lived long enough to be the mother of Malcomb Clark Middleton. (Mary Clark's father was Malcomb Clark and her mother was Nancy Buie Clark.) That sister was Jeanett/Jannett Claark. In Cumberland County, NC where the Clarks lived there is a marriage record for a James Basket who married Jannett Clark. In Mary Clark's will she mentions Malcomb Clark Basket, alias Malcomb Clark Middleton. I can not explain that one unless the marriage record should read James Basket Middleton which would match the James B. Middleton mention in the same will.Thomas and Nancy Basket had the following children for sure, maybe others; Odie Middleton Weaver, Nancy Middleton Ford, Mary Middleton Bailey (wife of William Fleming Bailey JR), Sarah Harrison (wife of John Harrison), James and probably Thomas JR. There are probably others we have not found. I also doubt the connection to the "famous" Middletons. Yes, Thomas did go to Ohio according to the letter from James Heaton. William Basket SR was living in Bute Co. when he died in 1764 and Elizabeth Basket is on several tax list for Bute/Warren County. I have his estate inventory and interestingly one of the slaves that James bought at the estate at the time of settlement is a "boy" named Moses who is later bought by Thomas Middleton when the James Basket SR estate is finally settled in Newberry County thirty one years later (this time referred to as "fellow").
I've tried to address each issue mentioned in your post in the order that you wrote.