My boyfriend told me that if I ever left him he might get the nerve to kill himself

Grace
Our relationship is having trouble because he is really depressed and won't seek help. He's been suicidal in the past but never had the nerve but said along the lines that if he lost me he might get the nerve. Idk what to do because I don't really want to lose him and I do NOT want him to die, but this relationship feels toxic and is producing more bad then good I feel. Any advice? I feel terrible