It sounds like your dog is having major separation anxiety when you folks are away from the house. Have you considered adopting another dog so that he'll have a companion again to help ease his loneliness while you're out? His lab companion apparently kept him happy and well-behaved while he was alive. It may just be that your dog really needs a pal around the house.

If that doesn't work for you, it may be necessary to find a doggie daycare where he can get the companionship he needs during the day.

Laurie

How much exersize does the dog get? How many walks a day?

I also wonder if a second dog might help. No guarantee, things could get worse. Maybe a mid-age dog, of the opposite sex, and with no issues of its own, not any larger than the first dog.

P.S.
This is the first time in ten years I typed in the Message box, that there is no cursor to tell you your current position. And quite a few of my recent posts are double-listed.

Poor guy;
he's out of his mind with grief, just like anybody else who's lost a longtime compantion.

Yep, he needs a friend/companion/pet.

Rescue Remedy after a good long walk before you leave the house

I saw two other products metioned on another dog site: Quiet Moments and Calming Aid Gel for Dogs. Haven't tried either, but it's good to know they are available (Calming Aid I believe was available at Petco). The products were being used for a dog who feared riding in the car.