I am so sorry this has happened to your pup. I'm glad to see you were able to get him the help he needed as soon as you did. These products do have some nasty side effects. It can effect a pet neurologically among other terrible reactions. Some pets are effected worse than others. If you google "Advantix warniing" you will see you are not the only one this has happened to.
This needs to be reported as soon as possible. This is the only way these companies can track the adverse reactions.
Reporting Pesticide Incidents
This is a wonderful site to get valuable info.....
Pesticides, Flea Meds, Heartworm Meds and Dog Health | Truth4Dogs
I hope your little one is feeling better soon.