Print all his e-mails and other correspondence. You need to keep documentation of his craziness so that you can get a restraining order if necessary.
De-friend (not just hide) him on Facebook (for both you and your son), block his e-mail and phone number. Let you older son know that this man is dangerous and that he is not to have contact with him under any circumstance. If he has a key to your home have your locks changed. Stop going to your mutual church and start going to your old church. He WILL try to contact you. Make it extremely difficult if not impossible.
Please do not worry about what he is saying to other people about you. If someone knows him and knows you and takes his side they are definitely not someone you want in your life.
Again, he will try to weasel his way back into your life. Make sure he stays gone!
I have saved all of his psycho emails from this morning. The guy literally went from practically begging me to call him at 1am this morning to saying nasty things to me and calling me names by 4am. He was pissed at me? I'm just living life with 3 kids and he sleeps all day til 2pm and was pissed cause I hadn't talked to him AND I was cancelling out on seeing him today. I had been going over there sometimes on Thursdays while putting both my girls in child care (one is 8 and homeschooled) just so I could be with him. Anything I did was never, ever enough. I did so much to make myself available and he would go hours between texting me and ignoring me like crazy then turn around and say I did it to him. He said I made him "chase" me. That is so far from the truth. I think the fact that he started to see that I "figured him out" was really what did it for him. That made it easy for him to finally get nasty and break it off as well. He will never contact me again, I am totally sure of that. I just know. I can tell. I have a feeling. I trust my gut on this. I know he won't. I have had a couple really good friends step up and be there for me today, one is a man and yes he is a man I knew "before" this guy and he is at my old church and I don't plan on doing anything like a rebound, but he has been wonderful!!! I am so thankful.