Help! I'm Scared...

I finally got the courage to let go of this creep. He was cheating (once again). I confronted him. He even called the stupid girl and wanted to put her on the phone with me to say they had nothing going on. I got into his voicemail and heard her messages. She knew about me and didn't care. When I hit him with that bit of information, he lost it. Long story short, he called me with the girl and basically made fun of me and mocked me, while she laughed. I couldn't believe it. This happened about a week ago and I have not shed one tear over it. I'm done. I finally see the real person under that mask and want nothing to do with him. I have not had contact with him since and don't plan to ever speak to him again in this lifetime. I blocked him from being able to call my cell phone and this has him in an uproar. He keeps calling my house phone and job phone, leaving nasty messages. He keeps saying "yeah, sit your ass down and cry". I used to cry a lot and I think this time around God has dried my tears and got me over it. We have a 12 year old son together. He even reached out to my son on Facebook this weekend and told him, "your mother is a piece of shit". "she's mad that she can't have me and she will never have me because she is nasty". I don't bother him. I won't respond to anything and now I won't allow my son to answer his calls. Should I be concerned or will he eventually go away? I have NEVER seen this side of him. I don't want to live my life in fear and this is how he is making me feel. Today kept looking over my shoulder coming home from work. Why is he being such an ass? I accept the fact that it is over. I let go. Any advice is appreciated.