Thanks for you question.
One thing that comes to mind regarding a protruding belly button is something called umbilical hernia. Umbilical hernias are more common in infants but can happen in later life. They can be caused by weight gain, obesity, ascites, coughing, and heavy lifting. In adults there is usually not a whole lot of discomfort but they can be sore.
As far as hair growth below your husbands navel, I think we're talking about two different issues and they are not related. Hair continues to grow throughout our lifetime. And even in later life we can grow hair where there used to be none. Frequently noted among men as new growth on backs, necks, abdomen, and nose and ears.
Here is some more information on Hernias. It talks about both types in children and adults.
I hope this helps. Please let me know if you have any other questions.
Winky your already tried was not visible when I wrote this.
What did the MRI show and why was it ordered?
Winky does your husband look like any of these images?