I can definitely give this a try, as I don’t know what else to do. However the fish was treated with prazi already in 2 doses 5 days apart. This was only a week ago…I'm not sure what to make of the video - seems like the fish has some patchy light discoloration as well. Before euthanizing it, you should try a 5 minute FW dip. That has some risks, but if the fish improves after a day or so, you can pretty much figure it has flukes, and can then treat (with praziquantel or hyposalinity). With really bad flukes, a FW may be fatal, but I don't think you have much to lose at this point.
Jay