Your husband sounds like he has low levels of magnesium. All mercury toxic people are to some degree because hg interfers with mg absorbtion and you also need more mg when detoxing and if he used DMSA that also binds to mg.

suggested amounts are 600-800mg per day in divided doses. Bedtime is your lowest point and then in the morning.

I also had slow recovery progress, but at 13 months I started to see things improve. I'm 19 months post removal now and much much better. Try not to get discouraged.