Help my dog hates being left alone. We've had him for 4 years and he's not getting better. I have tried everything. When we leave he howls adn cries the entire time we are gone. We have to crate hime because he'll destroy the house is we don't.

In the past 4 years he has done the following
destroyed 2 human beds
Eaten our sofas
bitten a door knob to the point that it's punctured
escaped out of his crate w/in 10 minutes (we now zip tie it shut)
broke his bottom canine teeth down to the gum line
cracked his upper canines
destroyed his crate w/his teeth and snout
pees in the house if left alone
has now started to poop in his crate
and other things I have blocked out ....

We cannot tie him outside or kennel him outside. He freaks out even worse. If we take him to the park and have to tie him so we can push the kids on teh swing he eats through the leash. We now have a chain leash.

The vet put him on a med but it didn't work.

He is not left alone a lot. If I can take him w/me places I do but he can't go to the pool or in the car on hot/humid days. He's not alone for a long amount of time 4 hours is tops and that only happens on a rare occassion.

Other than the above behavior he's a good dog. He loves my kids and cat. Is good w/everyone he meets but whoever his 2 previous owners were they really messed him up. He travels well in the car. He's super smart. This is his only bad behavior. He was a 2xshelter dog w/in a years time. Humane Society couldn't give us any information on his past family life.

Help please. I'm at my wits end