I do not believe there was a Daniel M. Waller and the "M" was a typo on the marriage record. Again, Daniel uses the initial "H" on the 1860-1900 census records.

Daniel and Lucy get married in 1869, a year before the following census. Lucy was age 16 on the marriage record and age 17 a year later on the 1870 census. Dan and Lucy are living with his parents.

1870 Columbia County, AR Census
Waller, James, age 62, Farmer, GA
Waller, Susan, age 52, GA
Waller, Daniel H., age 21, AL
Waller, Lola D., age 15, AL (Daniel H. Waller's sister)
Waller, Lucy, age 17, LA (this is Daniel's wife, Lucy O. Long - correct age and birthplace)