In my 30s and 40s were the constant migraines that had me wondering if I was a fit mother with all the time in bed. When I turned 50 I had grave's disease, (the thyroid goes supernova burning itself and me out). That is when the constant pain and fatigue dug in for the duration. We would deal with one problem after another but not get to the bottom of it. Killed off the thyroid--before it killed me--but had layers and layers of things that just went haywire.
I too am sorry your husband is so young with this! There isn't an 'average" age that I'm aware of and it is so different for each person that some say it gets worse with age but others do better after they find ,(by trial and error), what works for them. Sometimes weather changes or stress can make a person have a terrible flare, you'll just have to try different things. Wish I had a magic wand for you, but don't loose hope, it's overwhelming at first. Read all you can, find a doc that treats FM and be open to supplements. It usually takes a lot of little things to find some kind of balance.