Yes, I agree with everyone above.  He needs to have his Bile Acids Tested.  The amount of pups with Liver Disease (LS and MVD) is so unbelievable these days, that I am kinda shocked that this Vet is not pressing about it.
 
Please do not wait for another seizure.  Honestly, if this were my pup I would be finding a Vet in the area that has a better handle on the small breeds and one who know more about Liver Shunts. 
What food are you feeding him?  What treats?  Does he have any odd behaviors? 
... 
 
  
 
 I just went back and read your first post, IMO this has to do with his liver and I would be getting him into a Vet for a BAT ASAP 
