What is the ruling on the 100 dinars that the husband won from the National Bank, knowing that he was not required to keep an amount in the account to enter the draw?

It is not permissible for a Muslim to open an account in an interest-based bank except out of necessity. In such a case, it must be limited to a current account, not a savings account. The unlawful amount in the account is not permissible for your husband to benefit from, and it must be disposed of by spending it on the welfare of Muslims or giving it to the poor and needy.