My birth giver is pissing me off!

I'm working to get my 14 year old brother in therapy. I have custody of him and my mom is mad about it. She lost custody for being a shitty abusive mother who let's grown men and her female best friend molest my little brother. She's a crappy unfit parent. She acts like she cares but she doesn't. She beat my brother every day and allowed him to be sexual abused. When all the abuse led to him wetting the bed she abused him every time he wet the bed and called him disgusting. He has a huge fear of men and older women and even though my boyfriend would never hurt him and even had a heart to heart with him, my boyfriend knows he's still uncomfortable and is moving out so he can adjust. I asked my mother for his birth certificate and social security card and she's not giving it up. She claims she will need his social to claim him on her taxes next year. He doesn't live with her and hasn't for a little bit so why would she claim him on he taxes? His has his social memorized but we still need those things. Now she's saying she will give them to me for $200. She's claiming his birth certificate was $150. Bull fucking shit. I'm trying to stay calm because I can go off, but my brother gets scared. He's already going through a lot and has been extra emotional because since he keeps peeing through his goodnite (he wears them because he has super sensitive skin and wetting the bed irritates it) I took my aunties recommendations and got him Baby pants(plastic pants that you put over a diaper or pull up). That really made him sad and cry and I didn't understand why because he didn't cry with his goodnites. He's really emotional. Anyway back to my mom. She's trying to charge me to give her son his documents! How... Pathetic can you be. He refuses to talk to her. He just talks to his dad on FaceTime who lives in another country. I may just have to pay to get him a new birth certificate and social but can't she get in trouble if she claims him if she hasn't had him?