I had a similar problem when I first adopted my Harrier (also heart worm positive). As after the HW treatment she was going to need to be confined for 30 days and as she would have nothing to do with a crate and trashed the blinds when left, I was advised to delay the treatment for a week or two to allow her to settle into her new environment. I moved everything that she could trash out of harms way, and while I was at home, closed her in put a couple of my husband's worn socks under the door and put the radio on in the kitchen where I was. I started at 15 minutes at a time and worked up from that, closing her in several times a day (it was a three day weekend which helped). Once I got to being able to leave her for an hour, I would go and potter put in the garden so the only sound she could hear was the radio. It took about a week or so, (the shelter told me it takes about two weeks for most dogs to acclimatize to a new environment) and I can only assume that she associated the radio being on the the scent from the socks as someone being in the other room. We got through the heartworm treatment confinement (she is now completely healthy) and she became completely relaxed when left. We also eventually got a second dog.

Oh No!!! Since he seems to enjoy the kong, my suggestion is to stuff the new kong with his favorite treats and place in freezer for a few hours until its frozen solid. This will make the stuffing last for a long time and usually ends with the dog licking himself to sleep. I hope this helps!!!