Sounds like a terrible nerve irritation; nerve pain.
I would recommend taking him to get emergent care.
It's the nerve, the pain from the original extraction site can travel all over the place. Go to your family doc as an emergency "squeeze-in" appointment, or drive to the dental office to see if they are open, and if not, then go on over to the ER. Even tho the pain undoubtedly is connected to the extraction, there is a possibility an infection has set up shop and has formed an abscess in the back of his head, which is not good, and also to get better pain control than what your husband has now. I might add that whenever I have major tooth pain, and it takes me a while to see the dentist again, I'll drink DECAF green tea, it helps support the immune system if there's infection, and I'll shake out a few whole cloves from the seasoning shelf and put that on or near the extraction area (the numbing stuff in cloves will travel to wherever the pain winds up). Hope this helps, he must see a doc today or tomorrow at the latest.