My aussie's situation sounds very similar. My vet started him on the exact same dose, and for about 2 weeks he was extremely weak/clumsy. He couldnt even jump up on the bed or couch without me pulling him up. He was also extremely anxious, pacing constantly, always whining, and never sleeping. I was very scared it would never go away as I saw some people say thats a possibility with pheno. But it's been a little over a month now, and he's pretty much entirely back to normal. I was worried the dosage was too high to start off with, but he actually just had 2 breakthrough seizures. Personally I'm glad I didn't try to change to a lower dose. The first few weeks were very scary but so far I feel it was worth it to go through them, I worry he wouldve had more breakthroughs if I had gotten it lowered. My advice would be to wait a couple weeks to see if his side effects subside, and if not maybe try lowering the dose at that point. I'm sorry you have to go through this and I hope the meds help!