As you can see it is mixture of all combinations.
Biography is mainly on Level 2 (== Biography ==), a few thousand on L1(= Biography =) and L3 (=== Biography ===), and a few thousand without space(==Biography==). Since this has no visual effect, I wouldn't bother with them.
Same goes for sources. With sources, there are two texts (=== Source ===) and (=== Sources ===), but again no point in changing that.
So the only errors to check would be:
There are instances like this and shouldn't be.
== Biography ==
== Census ==
=== 1850 United States Census, 1850, Database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MCD2-6T2 : accessed 17 June 2015), William Giffin, Knox county, part of, Knox, Tennessee, United States citing family 643, NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.). ===
=== 1860 United States Census, 1860, Database, FamilySearch (https://familysearch.org/ark:/61903/1:1:M8TP-87R : accessed 19 June 2015), Nancy Griffin in household of William Griffin, 14th Dist, Knox, Tennessee, United States from 1860 U.S. Federal Census - Population, database, Fold3.com (http://www.fold3.com : n.d.) citing p. 150, household ID 947, NARA microfilm publication M653 (Washington, D.C.: National Archives and Records Administration, n.d.) FHL microfilm 805,259. ===
== Marriage ==
=== Marriage Certificate Tennessee, County Marriages, 1790-1950, Database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:XZ44-C47 : accessed 17 June 2015), William Giffin and Nancy King, 08 Sep 1843 citing Knox, Tennessee, United States, county courthouses, Tennessee FHL microfilm 1,205,071. ===
== Children ==
=== Death Certificate of Leander Tennessee, Death Records, 1914-1955, Database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:NS4F-V2K : accessed 17 June 2015), Nancy King in entry for Leander Dowell Giffen, 13 Sep 1934 citing Cemetery, Mt. Olive, Knox, Tennessee, cn 20756, State Library and Archives, Nashville FHL microfilm 1,876,817. ===
=== Samuel Benton's Death Certificate Tennessee, Death Records, 1914-1955, Database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:N9BM-KXL : accessed 17 June 2015), Samuel Benton Giffin, 23 Dec 1940 citing Cemetery, Knox County, Tennessee, cn 27895, State Library and Archives, Nashville FHL microfilm 1,876,894. ===
=== Daughter Eliza Katherine Wilson's Death Certificate Tennessee, Death Records, 1914-1955, Database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:NS7K-XZP : accessed 29 June 2015), Nancy King in entry for Eliza Katherine Wilson, 21 Dec 1945 citing Woodlawn Cemetery, Knoxville, Knox, Tennessee, cn 25920, State Library and Archives, Nashville FHL microfilm 2,137,365. ===