Given that your #438 comment said you weren't upset and that you were laughing, I think you would find it difficult for to convince a lawyer that you have taken his comments seriously. Add to that, you are posting effectively anonymously so how have you been slandered?
And good luck getting a court order to get the IP address on that basis.
And even if you do, good luck getting the telco to give up the details.
Don't take the forum seriously, I don't know who you are and don't care, and I think most people don't know who you are and don't care. Just keep feeding him and he will keep coming back at you.
It's actually good entertainment, keep it up.