I haven't had this happen to my kids, but my brother and myself use to get febrile seizures very often as young kids. I was the oldest, and very young the first time it happen to me. My parents were entertianing guests and heard me crying, and by the tone knew something was wrong. They came into my room and I was shaking, eyes rolled back, and vomit, coming out of my mouth. They ran out of the house, without saying a word to there guests, and raced to the hospital. Once I stopped shaking in the car I became very quiet and still(which scared them even more)but ended up being fine. I can say that no matter how many times we got a febrile seizure, it was always scary for my parents and we were usually brought to the hospital. I remember watching my younger brother go through seizures when he was sick and having my parents race him to the hospital each time.
I feel for you, and I'm sorry you had such a rough week. For some reason it seems that once they start, your more likely to have a seizure with even a low grade fever. I know, I'm not giving you great news, but they do go away (I think ours did around 3 or 4) and I'm hear to say that we are both fine.
It's hard to stay calm, but try to remember that some kids bodies just react differently to fevers and that he will be ok.
K.