Everything you are going through is normal, which doesn't mean that it's not incredibly hard to deal with. Your husband is having to grovel to social workers to get custody of his own child, who has been illegally and immorally kept away from him for years. He's in an emotional hell and he's reacting by shutting down. While that may be objectively understandable, it's very bad for your marriage and your family. But there's an end date to this purgatory. Once your stepson is in your home and you are mothering him, you and your husband are going to have more control over the situation and the good habits that you've built as you coparented your daughters are going to help you successfully parent your new addition.
With regard to all the previous posts:
They really, truly are trying to assist you here and make this as easy as possible for you. Listen to what they have to say. Even the things you may not want to hear or don't like. There is a lot of wisdom in their experience and it should be heeded.
The system is overburdened, underfunded, and sexist. If you want to get custody of your stepson, then you need to operate smoothly within this corrupt system. Rage all you want here. But take the advice, and win in court.