I need HELP on how to break up

After 15 on and off years of a terribly high and terribly low relationship, I can't take the emotional beating and disappointment any longer. I feel broken; shattered really but I want to be free. Currently I am "fooling the fool" and playing along nicely. I need to break it off. Do I just make a call, do I do it in person? I need to do it soon because this pretending is making everything worse. I am not good at pretending. He is being so super sweet to me after ripping me a part last week. This is the last time. I know more about his condition and I have seen it too many times. I finally was able to take my emotions out and see the truth of who he is and now I want to be free and heal. I have done some prep work when it comes to my work and I have support from my company. I know he will try to ruin at credibility I have but the ones that are important are all prepared and on my side. I am afraid of his rage and honestly not really sure if I can endure it anymore. I almost want to call and be simple and then say goodbye and block his number. Or should I do the break up in person. All advice is welcome. Thank you!