You'll feel a lot better when you start making better choices and start treating others the way you want to be treated. When you abuse others, you are abusing yourself.
Let go. He's gone, and sounds like good-riddance. The harsh reality of life is that anyone can leave anyone for any or no reason. Afterwards, moving on is the only solution. I'd get off FB, for one thing.
My life got lots better when I started praying for happiness for my ex. The only way out of misery is to wish the other well, and let go. Forgive him and wish happiness for him. It's the only way.