It does sound like he has separation anxiety. Symptoms do include destructive behavior, excessive barking and elimination issues when left alone.
There are some things you can do to help dogs who have separation anxiety. First thing is to take your dog for a nice long walk before you leave, preferably 30 minutes or long. Make it a long, quick paced walk to tire your boy out. Second is to use a low-key approach to leaving the house. Ignore your dog before you leave and after you come home for at least 5 minutes or more. If your house is like mine in the morning everyone is running around getting ready to leave. This has the dog in an excited mood and then suddenly he is alone. If this is the case, put him away from everyone, say in a bathroom until the frenzy is over.
Don't punish or shout at your dog when you come home and find he’s barked the whole time. When you do, you increase his stress level rather than reduce it. I'm going to suggest crating him since he is used to be crated in the car, so being crated at home shouldn't be too much of a problem. If he does end up eliminating in the crate, he will be uncomfortable and hopefully won't eliminate in it the next time. We will deal with the barking issue in the crate further down.
You can provide him with small stimulating toys or toys that you can fill with treats. Kongs with treat compartments are a good choice. You can fill them with peanut butter that does not contain Xylitol or yogurt and freeze it. It will take a dog an hour or more to get the treat out. If his mouth is busy he won't be barking.
Sometimes leaving a TV or radio on can help a dog with this problem as well. I have clients who have found taping the noise of the shower and playing it back when they are gone sooths the dog since they are used to being left "alone" when the owner is in the shower or bath. Also remember to not reward a dog's excitement to you with petting and affection or even eye contact. You want to show him nice calm praise when he is being calm.
Another thing that might help is a DAP collar. These use a pheromone to calm a dog. See one here:
Practice putting him in the crate, leaving the house, opening the door immediately and rewarding him with a hot dog treat if he did not scratch, bite and carry one. This teaches him that you leave but come back quickly. Once he seems to not do anything when you initially leave, lengthen the time he must be quet for you to come back in. Change the time as well. Make it 2 minutes one time and 10 mintues another, so he never knows if you are gone for an hour or gone for 2 minutes. It helps him stay calm for longer periods of time, just be sure you reward him when he is good.
Another thing that helps is to do things that might make the dog feel you are leaving and then don't such as putting on your coat or picking up your keys. Or leave without doing those things. This helps remove things that might trigger the dog to become anxious.
These should help his separation anxiety and boredom and help curb his barking. It will not be an overnight cure and will take work on your and your family’s part to be consistent in your interaction with him. Here is a site that also offers idea to combat separation anxiety.
There are many other methods available such as citronella spray collar, or shock bark collars that will stop excessive barking. Many owners feel shock collars are not appropriate, but a citronella collar uses a spray to stop the excessive barking. The ultrasonic collars are not effective so don't waste any money on those. They may work for a day or two but a dog learns quickly to ignore them.
Another option is medication, which is discussed on this site:
While medication can be helpful, you don't wan t your dog doped up all the time. The training works best for long term results.
I hope I've given you great service. If so, I'd appreciate a 5 star rating. The rating should be based on my answer and not any site issue. If you expected something different from the site, please don't rate my answer lower as a result. If you have any other questions at all, please reply here and I'll be happy to follow up with you.