You are more likely to get helpful comments about technical aspects of QDROs on this board. For my part, issues about what is fair with respect to dividing assets or not are not matters that have answers that can be given from afar. Fight about that in local court.
As to the technical issues, the stream of retirement payments for your life can be divided prospectively any way the court approves, including initial payments that are increased for some time to make up for past payments that were not divided. Yes, you can argue that the delay that caused those payments to slip by without division is the former spouse's fault and it is unfair to go back and retrieve them, but the federal law about QDROs is indifferent to fairness. That is a matter of state domestic relations law and a competent local lawyer is your best bet but will not be able to perform magic.