Training: Separation Anxiety

Hi All!
So I have a year old Lab, named Kingston. He is the most well behaved pup in the neighborhood, he's a trained hunting dog and even knows his lefts and rights. He's very intelligent (as most Labs are). Anyway, the only thing we can't break him of is his separation anxiety. I know most labs go through it, but does anyone know how to break it? We apparently upset someone near-by, as we received 2 notes (one on the garage door and one on the front-in the same day) stating this: "Shut your dog up or will report to HOA and Police" (I know, nice neighbors huh?)...

The next door neighbors told us he's not bad, but he does howl and cry for hours...

Anyone have any suggestions? We cannot leave him alone in the house because he shreds everything, we obviously can't leave him outside, so we unfortunately are forced to kennel him while we're gone. I feel so bad!

Thanks for reading!