I would pass on the fresh water bath?
I would lose the rid ich and go copper or just keep at the hypo and try the transfer method also if possible?
I like rid ich but marine ich is not freshwater ich.
Only 3 ways to kill ich on fish;
Marine Ich - Myths and Facts | Reef Sanctuary
The tank can rid the ich by running fallow for atleast 30 days...(timing will depend on many variables).
The butterfly won't last long not eating IMO