Right now is not a good time to get a second dog. This seperation issue actually needs to be addresses or you will probably have 2 dogs doing this behavior instead of one.
This dog has been through a lot of change and that's going manifest itself in many ways. Seperation anxiety is one of the more common ways a shelter dog deals with the change.
There's a book that's not very expensive called 'I'll be Home Soon" and it addresses this issue. Yet, you probably don t'ahve to go that far with this guy. The bahavior isn't habit quite yet. So, instead you have to make you laving and coming home a no big deal event. In order to do this, you have tone down your departing rituals (don't pay too much attention ot the dog before you leave), give him something to distract himself with about 5 minutes before you exit your house (A kong toy filled with frozen chicken broth and kibble), and just go. Don't let your husband pay too much attention to him either durign these departures and shortly after. Then upon your arrival home, dont' greet the dog first (I know it's hard, but trust me please). Check the mail, grab something to drink, Sit down on the sofa and then calmly call the dog to you for a relaxing snuggle in front o the news.
The whole idea here is to remove the adrenalin and emotions from the leaving and coming home transitions. It's tough, but if you are consistent and calm, cool and collected, your dog will mirror that mental state and will gain confidence in the routine and will stop the anxious behavior.
Also, quick trips (say 5 or 10 minutes) on the weekend where you leave the treat with the dog and return while he's still eating the treat help as well. He gets used to the idea that seperatiosn are part of normal life and you will be back.
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Chelle and the rest of the crew including, but not limited to Kita and Taiko (the shiba inu wrestle maniacs), Adi (reserved and dignified tabby cat), and all 28 reptiles