Because the federal government does not recognize same-sex marriages, there are actually two separate issues going on here. The tax refund interception is actually being done by the Department of Revenue, Child Support Enforcement Division ("DOR CSE"), which is a Massachusetts state agency. They can intercept any tax return that is due to your husband, whether in his sole name or joint. I am unclear as to how you have filed a joint federal return in the past, since the federal government does not consider same-sex married couples in Massachusetts to qualify for married filed jointly status. But if they were intercepted, it was not by the IRS but by the state-level child support agency. You may have gotten a notice from the IRS informing you that DOR had intercepted the payment, so I can see why it might be confusing. It was really the state. As a side note, there are administrative avenues to challenge the interception of your portion of the return for his child support obligation. The Massachusetts DOR CSE website could be helpful on this issue.
The unfortunate fact remains that the feds do not recognize same-sex married couples as married, and thus will not include your income, or any spousal benefit, in any of the SSDI payments made to your husband. In the eyes of the feds, it is as if you are roommates and have no legal obligation or relationship to one another.