If you end up trying to block his IP, don't just DROP or REJECT his packets. TARPIT [1] them! This way not only would you be denying him access, but you would also be draining his resources.

Another thing to try is to see just how much data his server will take. See if you can send him a GB-sized response.

[1] http://www.netfilter.org/projects/patch-o-matic/pom-external...