Time to leave!?

I’ve been with my partner for 5 years now on and off. I will always always have love for him and I will never stop caring about him but I don’t think I can be in this relationship anymore for so many reasons. He’s very emotionally abusive and toxic and I know i need to leave him but he is such an unstable person that I’m scared what it’ll do to him if I left. He has had a terrible life, been through stuff no one should ever go through and so he is such a sensitive person and I’m so scared that leaving will push him over the edge😢 what should I do?