Hello. I would suggest you do some reading at your local library or even on the internet.
I recently heard a man tell the story of his great grandfather who had been at Camp Douglas. I was amazed!
He spoke of the way they tortured the prisoners including running a knife along their necks and pouring warm water running down to give the feeling of cutting their throats.
From what the man said, many things of torture were done to the prisoners for the enjoyment of the guards.
The fact that your ancestor lived just to come home and die tells you how much the poor man lived through.
I have heard it said that Camp Douglas was as bad as Andersonville but with one difference. The food that they had and supplies were withheld from the prisoners and even Lincoln knew it was happening. I have read that the men lived on rats for the most part.
At Andersonville, the men were not provided for even when the Union prisoners themselves wrote asking for supplies from the Union army. The Confederacy did not have the supplies to give.
Camp Douglas was a terrible place because the higher ups wanted it to be. The Union had the supplies but withheld them for the cruelty of it.
Andersonville was a terrible place because there were no supplies to give to anyone including the guards who are said to have starved right along with the prisoners.
One thing I have never heard anyone say is that their ancestor was a guard at Camp Douglas.
My great grandmother's first cousin was at Camp Douglas and came home. He was young and strong when taken and that is probably the only reason he made it home.
You can thank the Good Lord himself that your relative made it home to die rather than be one of the nameless in some lot of unknown soldiers.
He had to have had a brave and strong heart to suffer that much and live to come home.
I seriously doubt that is what you had in mind, but that man should be
rememberd for being the strong man he was just to make it home to his loved ones.