The only thing that seemed to work for me was to remove the acropora and the rock it was on. Remove the Acro from the rock and frag it. Dip the frag and remount it to a different rock. Add it back to the tank. I have found the adult flatworms die from the dip but the eggs do not. The eggs for me were always around the base of the acropora and near by on the rocks. This is why I remounted them on a new rock. I do not know of anything that can be added to the main tank to kill just AEFWs, all acropora have to be removed. You will take large corals and make them small frags again but they will regrow. You may even trash some that can not be saved. I have been dealing with these pests for more years than I can remember but feel I may have no more AEFWs
I also have a Yellow Coris Wrasse and Hoeven's Wrasse that alot of people say eat parasites. I can not say it they helped or not, but they are neat little fish.