What should a wife do with her husband who uses hashish and drugs, abuses her, threatens to kill her and take their daughter, when she loves him and does not want to separate from him, and wishes to raise their daughter with both a father and a mother?

Supplicate, for Allah holds the hearts in His Hands. Seek help from righteous people to advise him. If he repents, that is what is desired. Otherwise, living with him is evil for you and your daughter, and separation is preferable. It is recommended to seek khul' from him due to his abandonment of Allah's rights. However, if you see that enduring him and continuing in the path of his reform is possible, then you may do so.