It does sound like seizures of some sort, and sadly that can be very hard to track down a cause for. I have not heard of allergies causing seizures, particularly environmental ones - the smoke is likely an irritant, though, so keeping that out of the place for your own sake as well as theirs is best.

He is likely as confused by the seizures as you, so the extra clinginess is to be expected. Have you changed food or anything in his diet? Hopefully others will weigh in.

Did your vet discuss any anti-seizure meds for the time being?