This should be in either Dog General or Dog behavior, more will see in it Dog General though. This is Pet General and although dogs are pets this section is for pets other than dogs and cats, like birds, rodents, reptiles, horses, fish, and any other kind of pet.

I don't have too much experience with separation anxiety, but I know there are others here who can help you.

If he feels secure in his crate than I'd suggest keeping up with that. I've read that a lot of times dogs with separation anxiety shouldn't be crated because it will make it worse.

Keeping his time occupied will help too. You can fill a Kong with peanut butter or cheese, if you freeze it and give it to him just before you leave it will last him longer.

You could also leave a radio or TV on so the house won't be so quiet.

Also don't make a big deal out of leaving. The same goes for when you return. Just come in as if you'd only been gone for a few seconds.

Good luck and welcome to Pet Talk!