It's very nice to meet you. I'm sorry your husband is suffering so much. I'm not sure on the fMRI but they are wonderful for many things related to function. I did some reading and it sounds like this is still in it's infancy, more so than I realized.
Here's a bit of what I read for those who are interested: (paraphrased) The wonderful thing about it is it reveals function and not just a static picture. For now it sounds like most of it's uses are for imaging the brain during activity to locate areas that are active. It shows what areas are active when you think of someone you love, when you feel sad or someone pinches you. These capabilities have led to new knowledge in serious diseases and new forms of treatment. But it still has many limitation and bugs to get worked out before it goes 'out of the clinic'. One area that is showing promise is in lie detection. It's a spendy way of doing things but seems to be effective is showing if someone is being truthful or not. But the chances of it being admitted into a legal case are slim to none as it stands now.
If I may ask you a question....what type of pain does your husband have? Is it generalized muscle pain, specifically in a joint or one region? The reason I asked is fibromyalgia came to mind. That is where the body has generalized muscle pain that can be aggravated by temperature, stress of any kind and even weather. Not too much is know about
it's causes but it's very real and very painful. I know from personal experience. It's just a thought. You might jump over to our Fibromyalgia forum and do some reading there. It would give you a start anyway. If you think it's possibly fibro then a good PCP or rheumatologist who treats fibro would be able to diagnose it. Often people who have it suffer for 5-10 years before someone finally recognizes what it is since there are no blood test, etc for it.
I hope something here gives you hope. Please keep posting and let us know how we can help you and hubby.