First, think about everything you could be doing with your time and energy if you weren't dealing with this person.
Then, go about distancing yourself from this toxic person. I think it's time you "start seeing other people", if you know what I mean.
If it were me personally, I wouldn't worry about returning phone calls or replying to emails too quickly, would turn down invitations to do things that didn't truly interest me ("Sorry, I have other plans" or "Sorry, but I'm not interested" work well), and I would politely end any conversations wherein the other person starts becoming confrontational or abusive ("Sorry, but I need to go").