Oh my goodness, thank you for taking care of this dog!
I don't know if I misssed it, but were any blood tests done, to test liver and blood counts, a chem panel and cbc?
You want to hit this hard. On the tick list, the recommended dose is 10 mg/kg twice day, for 6-8 week min, depending on the above blood tests.
There I an overwhelming amount of info here!