Yes, I believe you are being unreasonable. ThemeForest items dont come with support. And the email he sent to you was perfectly reasonable. The dude is probably from Eastern Europe, so dont expect him to have perfect english. I highly doubt he was intentionally trying to be rude.
How long have you been using wordpress themes? It's pretty much DIY, paid theme or not. There's no way to get around having to fix things yourself when they break.