Should I write to my ex?

I think you are better off without this person in your life. He seems rather cruel and like the mentally unstable one. Strive to make new friends. If your old friends want to be part of your life, they will, but don't count on it. Often people disappoint and let us down. Simply strive to move on and expand your own social and personal realm. Things will get better, I promise you. Don't let this person have all this power over you anymore.