My husband got divorce many year ago because his ex wife abused their older son because he was bullying his brother.
My husband stayed with full custody of their older son (which is adopted) and 50/50 custody on their younger (biological one). 
After a few months of this incidents the ex wife took my husband to court to fight for oldest custody, and after a long battle (that let him with a huge amount of debt) he ended up with 50/50 custody as well. 

At first SS was happy to be with her, and he started being disrespectful to me and to the point where I don't feel comfortable around him, or him being around our 6 months old baby girl (considering that he acts violently with his brother, even chocking him not long ago) 

After 2 years living together, she got married to a man that has anger issues, which leads my SS to have problems on their household (SS threatened on committing suicide, and injuring animals and his brother)  this is why she started taking him to counseling and he was diagnosed with ADHD, bipolar disorder and no empathy whatsoever.

He is currently on a lot of medicines, and even when he has gotten better, the ex wife still feel not safe around him, which is why the doctor recommend it him putted on a group home. 

After that, my husband called the doctor and told her that he has no fear of having him in our household (without asking me how I feel). 

And the doctor gave the recommendation of SS living full time with us, so my husband gave ex-wife a call, they talk about it. 
And yesterday at the kid's exchange she ask SS, do you want to live with your dad, he said yes, so here we are. 
I feel not heard, I hate having to live uncomfortable and in contast worry about my baby. 
how to approach this with my husband??, I feel at a loss.