I think you may be getting some of your Delilahs mixed up.
1). From the 1860 Census in Telfair County, Georgia, district 340 Delilah, age 21 is living with her husband ALLEN Yawn, age 23.She could not possibly be the wife of Isaac Yawn (b. between 1780-1790) for a multitude of reasons.So it looks as though there were TWO Delilahs that married into the Yawn family.
2). Also, as I have stated numerous times, Isaac Yawn Sr. and his proposed wife Delilah are NOT on the 1860 Federal Census in Decatur County, Georgia.I suggest you take a look at the original census microfilm or the census images on ancestry.com.Whatever "source" you have saying there were there is just flat out wrong.The only Isaac Yawn "of age" in the 1860 Census living in the state of Georgia is Isaac Yawn, b. 1824, Georgia. I have looked over the Steam Mill precinct of Decatur County numerous times and Isaac Sr. and Delilah are NOT listed (Only Isaac "Jr" and wife Rebecca with children).
3). You state Isaac and Delilah were married in Decatur County.There is no record of this in Decatur County probate records...what is your source for their marriage occuring in Decatur County?
4). You site the family Bible of Chesley Allen Yawn as the source for listing Isaac Yawn "Sr" as a son of Simon.Are there hard copies of this that can be copied or is this posted on-line somewhere so it can be viewed?
4). Again, Henry Allen Yawn is not found in Decatur County in 1850, again you need to recheck the census records.He was with his family in Holmes County, Florida in 1850.
5)There are other Yawns in Decatur County (as early as 1830) including Martin, John, and Elwood Patrick...are they listed among the Bible records of Chesley Yawn?
6)I have seen the on-line version of the Giessendanner diaries.You state the Giessendanner diaries connect Isaac Sr and others to Nicholas. How is this so when the diaries end well before the birthdate of Isaac Sr?