It's great that the dog has a loving home - that is a good foundation to work from.
The mental stim stuff suggested can help, not least because everyone sleeps better when they have been busy during the day, and is good for the dog anyway because in all honesty it doesn't sound like he gets very much - so please look at that. It's not, however, a silver bullet.
At the heart of it, it sounds like the dog is scared to be left - this may be relatively new in a dog that was previously ok with it but that doesn't change the fact that it is how he feels now. It you come at it from that angle, it may help. If the dog is scared at night and you don't want him upstairs then can someone sleep downstairs with him for a few nights to see if that helps? Perhaps the full nights to start with but then leaving him about 6am, 5am, 4am and so on...
If that's not a goer then think about other things that help reassure when left alone. I had a dog that started crying at night as he got older and found leaving a light on for him really helped him. Leaving some relaxing music or a low level radio.
Giving him something he is allowed to chew can help. This will be even more effective if it smells of you (or your oh) so try spending a few days handling a chew to let it absorb some of your natural smell. Dogs chew because the very action of doing so is relaxing to them, it soothes the nerves.
There are plenty of people who think smells can help, just like with humans. Lavender scented oils left in the kitchen at night may help.
Dorwest herbs sell Scullcap and Valerian tablets and tincture which many people speak very favourably of (though I have never used them myself).