From what I have read, in Europe they use even higher doses of Amoxycillin with very good results. My son just spent 4 mos. on 7,000mg. (7 grams). He seems to have plateaued and his LL neurologist has just raised the dosage to 10.5 grams. I have heard of other people on another forum that have used even higher doses, so I am encouraged.
I hope the Amox. works as well for you as it has for Dan.