Custody of 18 months old male child and filing a divorce

I am in desperate need of help . My husband lives in Dubai and he abuses me mentally and physically . I gave him many chances but he continues with the same which has left me really depressed and in bad health , to the extent that I suffered headaches and giddiness all the time . I tried to talk to his family regarding the same but they always ask me to stay quiet and patient and not disclose anything to my parents . But a week before I tried to talk to him as why he harasses me all the time by saying that he doesn’t want me but only my son and asked me to leave and go to my parents house . He snatched my sons passport and locked the door keeping my son inside . I have to leave unfortunately without my son . He didn’t give me any money , no ticket , no taxi fare and even blocked my number . Now I need help we tried to talk to them amicably but he threatened us by saying do whatever you want to do I don’t care as he lives in Dubai . I want to seek my child’s custody and also want to file a divorce . Please help me how can I get my child’s custody asap as he’s a toddler and needs his mother.