Good questions. Marine ich generally can't be cured by "only" lowering specific density and raising temperatures. And, we know that the "horse is already out of the barn", so I would move your fish out to a separate system that you can treat them with a regimen of copper-based medication (and a test kit...) and let your main system "go fallow" (empty of fish hosts) for a good month (or two)to help the parasites to become less virulent. The mode of action of lowered density (1.010~1.018) water is the destruction of tomites via their inability to adapt to the reduced osmotic pressure. Raising temperature (low-mid eighties, 82~83) mainly speeds up metabolism, and hastens the process.