That's a good question, Paula. I'm sure you know as much as I do and probably a lot more. John, Jonathan and Elijah were specialties of Marsil and her co-editor, Bill Carroll. I did not keep detailed track of them except where Marsil asked for my help which was more re. the families who went to Illinois and I spent a couple days in Clay County while I was on vacation in Illinois and Indiana one year. I was surprised that "Creech Country" did not cover Elijah in the thorough way that John and Jonathan had been explained but perhaps that had been the agenda that Marsil and Bill had planned for the following. I agree about Stephen as their father.
I wouldn't put too much weight on the Lee County history. I was told when I was in that county that when they decided to publish the history, a person was assigned several names to work on, the information was not necessarily from family submissions. We know numerous errors have been proven in that entry. It looks like the person assigned to the Creech name worked hard on it and found quite a bit but what was out there at the time was often not very accurate nor taken from primary sources. It seems like a lot of Creech family members would have still been there to interview so I was even more puzzled by the problems in the entry unless by the last couple generations or so, the "real" story has become confused with what they've been told by others using faulty work. It's not likely that Elijah Sr. and Jr. both married a Nancy Spencer but you will find name duplications in more than one old work on the Creeches; it wasn't an easy task to keep names straight without the aid of computer indexing. But then there might have been several Nancy Spencers around, too.
Death certificates are only as good as the knowledge of the informants so ask yourself how much weight you can give to the informants on both your Martha's death certificate and on her brother Jonathan's. Were they family members, neighbors, doctors, who? Were they people who were likely to know for sure or not, especially since they gave conflicting first names for the mother?
All I know is that Marsil said Nancy Spencer had not been proved and she questioned whether Elijah might have married second to Sarah Elizabeth "Betsy" Lucas but that she nor Bill could find any documentation. She wrote that John Anglin's Deed by Heirs in 1826 seemed clear that Elijah had been married to an Anglin who was deceased by that date and that the deed signed in 1829 by Elijah and Sarah Creech could possibly have been Elizabeth Lucas but whom others have confused as Sarah Anglin, not having researched fully enough to have learned that Elijah's Anglin wife was deceased a few years prior. I guess I, personally, would have to question: then who was Nancy in Elijah's 1850 household and the widow in 1860? Did Betsy have a sister named Ann or Nancy and could Betsy Lucas have been deceased before 1850 and Elijah married a third time to Betsy's sister or some other relation? Or was there never a Betsy Lucas and she was actually Nancy Lucas (or perhaps Elizabeth Ann - one and the same)? Then who was Sarah who signed the 1829 deed with Elijah if his Anglin wife was deceased? Or was the 1829 deed another clerk's error when writing the name Sarah because he might have known Sarah Creech? I certainly wish you luck! Every question about Creeches seems to bring on three more instead of an answer, doesn't it? Or maybe some of these questions have answers now but I don't know about them, if so. I assume Lucas and Spencer research has not turned up any hints.
Have you tried posting your well-thought-out query to the Creech mail list? Perhaps Bill Carroll is still a subscriber and might have some suggestions.