So sorry... I know you must be so worried, I would be too!
I would definitely be on the phone with the vet or e-vet by now! And, I would absolutely follow whatever recommendation they make.
FWIW, my dog has never had a reaction like that to flea treatment. So, again, please continue to closely monitor your dog and be in communication with your vet or the e-vet. They will give you the best advice as to how to proceed.
Wishing you and your pup all the best!!!!