I may be wrong, but wasn’t the 2013 attack a chlorine gas attack? That would fit his symptoms a little better.
It says here that it was a Sarin attack and that over 1,400 people were killed:
http://www.bbc.com/news/world-middle-east-23927399
Thousands of survivors that experienced symptoms, so it would make sense that Kassim Eid would be one of those.