What happened to captured confederate Woodman Stanton in Tennessee after US Civil War

My ggf brother, Woodman Stanton, born about 1838 possibly in Montgomery or Dickson County, Tennessee.

In 1850:census he is in middle district, Dickson, TN. In 1860 census he is in district 1, Hardin County, TN.

He enlisted in the 52nd infantry TN in 1861. He was On leave to go home and cut wheat, and trying to return was captured by Union army in 1863. He was at Camp Morton, transferred to Camp Chase, then to Johnson Island in Ohio. He is listed as a prisoner of war in 1865, and released on oath of amnesty 13 May 1865.

I have a letter from the Washington DC file of Sec of War, Edwin M Stanton written by Woody. He claims to be related as a nephew, and mentions his father, Robert Stanton. He also mentions a brother in law, JR Cranford of Alabama. I have never heard of a Cranford. We have no proven relationship to Edwin M Stanton.

There is a possible marriage record of a Waddy Stanton to Mary Barnett on 11 Feb 1870 in Benton, TN, looks like signature is Woody. There is a W O Stanton, and a Will Stanton, enumerated in 1891 in McNairy County.

His brother, Benjamin lived in McNairy in 1891. ( Benjamin was a union soldier in civil war) a brother George W was a confederate, and died of wounds in Nashville, 1864. I find no other records.

How do I ascertain if this is his marriage record?

Where is he in 1870 and 1880?

When did he die?

Any gravestone?

Any children?