A mate would be the best solution ^^ but there are many other solutions which are easier.
You'd had to habituate your dog when he was puppy but by many reasons it wasn't possible. The first you must do is habituate him to stay alone.
Have you got a big window or a big glass door where he could look at you? Like this:
If the answer is 'yes', you must start with that window... go out and stand there while he's watching you. If he is relaxed (doesn't bark, scream, howl, etc) come back into your house and reward him with some treat and caresses. Next step is the answer "no" hahaha
If the answer is 'no', leave your dog in front of the door (indoor, of course), and then go out... he will smell you through the door. When you realise that he's relaxed (you can't hear screams, barks, or howls), come back into your house and reward him with some treat and caresses. He must feel that you're very very happy. You also can say him "Stay" or your staying command before leaving home. Do this exercise 5 times every hour.
Ok, the next step will be able to do when he were relaxed... the second day probably. He'll feel that you're there out and you'll come back if he's relaxed. Go out for some minutes, and pay attention to his behaviour (you could ask for help to your daughter).
If he doesn't get relaxed in 3 minutes: Come back into your house and don't give a damn about Nanook, just straight past to the restroom or bedroom. Wait a minute and call Nanook, then you can reward him (not much because he didn't it well)
If he gets relaxed in 3 minutes: Come back into your house, sit him and then reward a lot (because he did it well).
Following this pattern or standard exercise, increase the time: 5 minutes, 7minutes, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 1h, 2h, 3h...
Some more tips: buy a kong and let him play with it when you go out... he'll have fun for hours with his -full of food- kong.
You also could exhaust him before leaving (if you have got time to spend...)
And it's very important not to say "bye bye" or "hello" to your dog, just straight past. (It's theory because I CAN'T not to greet my dog when I come back home ^^)
I've forgotten another thing I wanted to say... If I remember it, I'll post it later. Good luck