You've been given some good advice.

I say, he should be crate trained, or left with a daycare when his owner isn't home. The only thing about daycares that I don't like is that some don't pay attention to the dog; just keep him in a room all alone, and some reward bad habits and untrain a dog.

I also reccomend vigorous exersise when possible. It will tire him out for a while and leave him calm.

There are lots of herbs out there that are meant to calm a dog. If you look up some herbal recipes for dogs, it's very interesting to read. You can also buy some dosages in pet stores.