What type of behavior does the pug exhibit when he feels separated from the family? Is it just barking, or does he do damage to the house?

It would take some time, but you could try crate training. My moms dogs know to go to their crate (they're small and share a large crate- they were separated but prefer to be together) when she's getting ready to walk out the door. They don't have access to furniture, so they can't scratch or chew our stuff up, and they don't mess in the crate because its their personal den space. It might help to drape a blanket over half of it too, sort of like we do for snakes. It sounds odd but the dogs don't mind it at all, and they go in when they're scared or sleepy. Just don't ever punish him by putting him in his crate, because he'll try to avoid it after that.