I think you just started a thread joygirl! It's amazing to me how many things become addictive and cause withdrawals, even things that we often think of as innocuous.
I'd enourage your H to drink lots of water to help flush out any toxins. If he's getting a lot of headaches maybe he needs to slowly wean from the caffeine rather than go c/t?
I'm sure other folks will be along soon with more info. and support. Take care.