That's unusual, but not impossible. There
seems to be different species of dinos that vary in toxicity, although I'm not sure if there actually is. Some people complain about extreme toxicity (like you're experiencing) while others have very mild toxicity. Maybe it is from inaccurate ID...who knows?
Anyway, that article I linked you to has a good step by step procedure for you although I think it doesn't put enough stress on the elevated pH. Elevating the pH has a significant effect, and is not to be overlooked. Kalkwasser is the easiest way to do this because it provides a steadier elevated pH than other methods. You will need to replace most or all of your calcium and alkalinity dosing with kalkwasser to achieve this. Make sure you have a
calibrated digital pH meter to check pH rather than a drop test kit which is not accurate enough. Check pH in the morning just before lights on and in the evening just before lights out. Once you have achieved a steady elevated pH then move onto the next steps of siphoning, waterchanges, carbon, black out, more waterchanges. Keep the pH elevated for at least a week after.
Here is an article by Randy Holmes-Farley that is outdated, and I think not as good as the first article I linked. However, it does give good advice for using kalkwasser to raise pH as well as calculations for you to do so at the end of the article, so check that out too.
http://reefkeeping.com/issues/2006-11/rhf/index.php
Good luck! This "algae" is no fun...