Hello, I have spoken to my husband about our separation and it didn't go in well. He abused me and t

Hello, I have spoken to my husband about our separation and it didn't go in well. He abused me and threatened me to leave my son and only then he will agree for a divorce. When i said i will have to take the matter to the court he started yelling and shouting at me and insisted that even he will approach court and make sure to bring me on road. Please advice in such scenario what should i do. The next morning when he was cool he agreed for a divorce and was even ready to give me my sons custody i even asked him to give me this in writing which he agreed but later very conveniently forgot. Since i stay abroad i am totally dependent on him. Also if he gives me in writing that he is willing to give me the custody of our son can he challenge it later in future or can his family has any rights to challenge his wish.