Sorry to hear that things are going that way. Few things you can do....
#1 Is blow it off...this may be hard to Type A personalities that get into this job in the first place, but basically look at it from the viewpoint that he's staying, you're going home. You are doing just what you need for your paycheck, nothing more. Who cares what an inmate says? If he's a problem, and there is the risk of complaint against you, let a sup that gets paid more handle the issue.
#2 Look for employment at another agency. I know this is not always ideal, or even workable. Sometimes you just might need a change. Do you have the option to try to go to the road? Dispatch? How about a smaller agency within your jurisdiction? The grass is always greener on the other side of the fence, and every agency has its BS, but sometimes it's just better for everyone to look for a agency that meets your style.
#3 Look for better or other stress relievers. When I had an issue with a sheriff who has since been voted out, the weight of the stress on me was very hard on me. I looked at the boards of Police One, Calibre Press, and others. I saw the different complaints that other officers had. It was almost cathartic reading these, as I realized there are some really fubared agencies out there and mine didn't look so bad. It also let me get stuff off my chest with people that knew where I was coming from, very much like you have done here. Sounds like you already have some methods forgetting rid of stress, such as the gym, but be careful that it does not affect your marriage, since you made the comment your wife doens't understand. She may not. But be careful, and don't tun to the booze. That also makes careers and lives tougher.
Hope you make it. I try and deal with how the BS is at my job daily, and somedays are easier than others. How you ultimately do deal with it will determine the length of your career in a time when no good officers wants the job it seems.