I'm just now getting back into genealogy and have to review my records and refresh my memory on just about everything.I want to let you know that I have been (and still am) interested in Micajah Brooks.You have a lot of information in your post that I do not remember, so I am interested in exploring it.
I too have looked for Micajah in 1840 and have not been able to find him.I tend to believe that he was still in Clay Co., IL at that time and the census taker just missed him.The family did move to Reynolds Co., MO apparently about 1849.He is found in the home of his son, Elijah Brooks in 1850.He lists his age as 96, but I'm not sure he knew how old he was.His wife, Rachael, is also in the home.Her age is listed as 100 (????).Rachael lists her place of birth as Penn.Elijah has a daugher, Nancy, less that a year old, who was born in IL.Hence I figure they had just come to MO.
I really question some of the info. that is out there, including some of the information in your posting.At one time I did believe that I might be a ggg grandson of Micajah, but I can't find proof.Moreover, recent DNA test results for me have cast even more doubt on the possibility.Still Micajah was very involved with my g grandfather Jonathan Riley (b. abt. 1820 in IN).He sold land to Johnathan in Clay Co. shorly before leaving for MO.It is also true that they were neighbors.
The possible connection to my Johnathan is that Johnathan could be the son of William and Thirsey (Brooks) Riley.Thirsey was very likely the daughter of Micajah, but even that has not been proven.There is just a lot of circumstantial evidence.
You can reach me at email@example.com if you would like to pursue this by e-mail.Or posting to this sight is also suitable.