We are pretty sure William is post-war since he died in 1969. He had not reached his 101st birthday.
Alpha was apparently pregnant at the time of the census because Jeff was born 1870 and is not on the census. Therefore James, being his father, must have died in late 1869 and DeKalb TX therefore seems a likely location. There are two other post-war children that should be on this 1870 census, but are not, so it suggests they apparently died before the 1870 census as did James. Maybe there was an epidemic? Or an accident during the move to Texas.
The net result of this is to rule out James of the 3rd Ark. Inf. as a possible, unless the death record is in error.