QDROphile is correct that most state, county and municipal plans are not covered by ERISA, the Federal law that normally covers pension and retirement plans adopted by private employers in the US. But I have seen some state, county and municipal plans that have adopted ERISA qualified Plans in order to facilitate ease of administration either in-house or by third party administrators. You used the acronym DRO and QDRO. The "Q" in QDRO stands for "qualified" under ERISA. So your first task is to see if ERISA even applies to your disability pay. If you didn't work for Marin County, and just mentioned Marin because that's where the Court is located, then you started off on the wrong track.
Keep in mind that the purpose of the DRO in you case is not to allocate "marital property" or "community property" between you and your ex-wife. It is intended to pay your ex-wife alimony (spousal support). If you are under ERISA this is a legitimate use of a QDRO. However, the question is whether or not under California law disability benefits can be the subject of a DRO at all, or can it exclude spousal support. My my home state, Maryland, disability benefits can be accessed to pay child support and alimony, even if they could not be divided as property. See Riley v. Riley, 82 Md.App. 400, 571 A.2d 1261 (1990).
And in the Supreme Court case of Rose v. Rose, 481 U.S. 619 (1987) - https://scholar.google.com/scholar_case?case=8800536124027399358&q=rose+v.+rose&hl=en&as_sdt=20000003
the question was whether a state court has jurisdiction to hold a disabled veteran in contempt for failing to pay child support, where the veteran's only means of satisfying this obligation is to utilize benefits received from the Veterans' Administration under 38 U. S. C. § 314 as compensation for a service-connected disability that cannot be divided as "property". The Supreme Court held that such disability payments can to accessed for child support. It is clear that the same outcome would apply to payments of spousal support.
Also keep in mind that a DRO/QDRO is an order entered by the Court and enforced by the administrator of the applicable plan. The administrator is authorized to do only what the Court has set forth in the DRO/QDRO. The administrator doesn't prepare the DRO/QDRO. Your comments about the plan administrator are just not logical.
All Court orders that are intended to attach assets via a garnishment or via a DRO/QDRO must state the amount or percentage of payments to be collected from the garnishee or Plan Administrator and the duration of such payments. Often the duration is "pending further order of the Court." There is something you are missing and the fact that you obviously did not have a lawyer representing your interests led to your problems.
DSG