If you don't have this man's service record, you might want to consider getting it through the link below.
Newton Van Pelt's Compiled Military Service Record (CMSR)includes the envelope and eleven (11) cards. These cards are primarily communications from the Georgia Confederate Pension board and Union Prisoner of War Records. In a nutshell, your ancestor was captured at Cedartown, GA in July of 1864. He was then transferred through Nashville, TN and Louisville, KY to Camp Douglas (Chicago), IL. He has a notation that he escaped, apparently temporarily enroute. He died from Smallpox and certainly must be buried in Chicago, IL.
The Confederate authorities were unable to find Confederate documents to confirm his service.
Hope this helps.