USFSPA law explicitly says that for DFAS to help, your decree must put your amount in terms of either a percentage or a dollar figure. If yours puts it in terms of months of pay, you may be out of luck in getting DFAS's help in payments.

If you didn't meet the 10 year rule, then DFAS won't help either.

If your ex has been ordered to pay and is not, I'd say you're in the same boat as any other spouse who is not being paid according to the court order. At the least your ex is in contempt of a court order. Depending on your state, they my have some garnishment options. You should certainly be able to request a hearing on a contempt charge and other means to get enforcement of the obligation.