Advice, police?

I am pregnant and my boyfriend just broke up with me, chose alcohol instead of me and child... but today when he sobered up he said he would get custody of her. So, I was wondering if I should tip the police on his brother selling and doing pills. If my baby is going to be over there, Ii would love for his brother to be gone. His brother has threatened to kill me if I ever called the cops... but he wouldn't know if I tipped them. Thoughts? I'm honestly scared more than anything. I wanted to stay with the babies father so I wouldn't have to worry about him drinking around the baby, since I'd be sober... :/ thanks in advance guys