I would consider suing his estate if it has any money, or I would contact the legal department of the military branch in which your ex was part of an consult with a legal advocate about whether you could file a claim giving that your ex failed to pay any child support. Also if your child has a permanent disability that prevents him or her from being able to support himself or herself, you should contact social security administration to see if your child can collect social security from your ex-husband's benefits.

You will have to sue his estate. In simple terms, when a person dies, the remnant of their property, assets, etc. is called their estate. Because a person usually dies owing debts or with obligations due, there is usually money collected or paid out by the estate. His child support debt is a now a debt of his estate, so you can still sue to get what's owed.

You might want to also get a Temporary Restrainng Order (TRO) put in place to keep his wife from maybe trying to move/hide assets if she thinks your coming after them. And of coure you'll probably have to do some tracing to find out how much money was there when he died, what happened to it, etc.