I give my 2 dehydrated sweet potato chips when I leave for work that keeps them busy until I'm out the door. They get it just before I'm going out the door. I've filled empty marrow bones with nearly overripe bananas, they fit nicely. I freeze them.
My dogs don't bark when I leave, to my knowledge. My sister used a citronella collar on her dog when she crated him. After one or 2 spritzes, she said he no longer barked in the crate, at all. No shock, only the spritz. I don't like to leave my dogs for long in their crates wearing a collar, so I'd try it on a day I'm not working so I'd only go outside the door for a short period of time, see if he barks, but not leave him all day.