That doesn't solve the problem of him talking crap on forums.
Ok I just payed him another 0.013 as he said thats all he asked and he'll leave me alone. I hope he keep his words.
DUDE! You are a sucker! He knows that, and he is going to come back and ask you for more, because he knows you will pay!
Let him DDOS your site if he can. It will cost him more money that it costs you, even if he has the ability.
Just ignore him and understand that if you shrink to his level and start calling him names, etc, that it will hurt your business and he will win.
I read all this and believe this tip is most effective and best for your work just do your work and leave this person and check what he can do just this is work for you to do