Labramutt experience.
Last year, my wife and I adopted a labramutt (mix of border collie, black lab, shepard, etc) from one of the local rescue agencies. He is a great dog, but he came with a severe case of separation anxiety. After talking to the vet, here is what we did.
Get a dog toy known as a "Kong". It is a rubber chew toy that is hollow and can be filled with things. Break up a few dog biscuits and put them inside. Make them small enough to come back out, but large enough that it takes a little work. Now, seal the end of the Kong with peanut butter. This will keep the dog quite happy, and busy, for at least 10 minutes once you give it to him/her, but don't do that yet. Once you have the kong loaded, take the peanut butter spoon and get a little more peanut butter on it, and put a "benadril" (pardon the spelling) tablet in it. Check with your vet, but I think it is one of the little tablets for every 25lbs of body weight. Give that to the dog, and once he/she has finished it off, give them the kong. By the time the kong is empty, the dog will have forgotten that you have left, and the drug will have started to make the dog sleepy. From there, it should be smooth sailing.
We had to do that to Bacchus for about 2 months (not every day, but fairly often), and he has been fine ever since.
Good luck, and get some sleep.
D