You say you don't know what is wrong with him. You have lost your son to a gang and drugs that is what's wrong with him. Right now he is no longer your son. You say you are afraid you will lose him and never see him again. You have already lost him.......not physically but he is not your son. You have two other children on the right path......does he dislike them like he dislikes his brother? Look at the danger he is putting them in. Sometimes we have to do hurtful things to save our children.
Please consider the children that are good and living in the same house. It sounds to me like you want to keep him in your life at any cost to you or the rest of your family. The sad thing is........you are not benefiting him. It is only what makes YOU feel good having him around no matter what. Step outside of yourself and do what is right for him not for yourself. I don't mean to sound harsh but I am the mother of a daughter who is addicted. She is young and pretty.........she is who pays your son's salary.