Being a Tanner, I believe, was one of the critical occupations, considered as providing vital military goods, which were exempted from military service by the Confederate Conscription Acts.

Also, being 42-45 he would have been exempted due to age.

So, on those two counts he most likely would not have had a military record with the Confederate Army as such.

Any records of his action would most likely appear in civil records such as contracts and court papers, since you say he was accused of being a traitor to the United States due to his occupation. I would research the Fort Smith Grand Jury Federal court records to see if he was actually charged.