Sorry to hear that he is having more seizures.
Remember that with KBr, the half life is somewhere between 4-6 weeks. So one week won't be enough time to really notice a difference in the change in levels. You could discuss a loading dose with your vet, so you would give something like double the required dose of KBr for a week just to bump it up quickly, then reduce down to the normal dose after a week's time. You would likely see an increase in side effects during that time, but it would get the blood levels up to therapeutic range quicker, and the side effects would decrease after you get back on the regular dose.
Have you had his thyroid tested and sent off to Hemopet? Even if the thyroid comes back "within range" it can still be too low for an epi-pup. Epileptic dogs need to have their thyroid levels in the higher end of normal, or they may not get adequate control even with antiseizure meds. Check out
http://hemopet.org for info on testing. You can either send the blood there, or have your vet do a 6-panel (4-panel is not sufficient) and fax the results over to them. Very often a combo of Soloxine and a low dose of KBr will yield better results than KBr or Phenobarb alone.
After that, your next course of action would likely be a combo of phenobarb and KBr.
Good luck! I hope you get this sorted out soon.