As for the salt, 40 pounds in a 6000 gallon pond shouldn't be but 0.8%, assuming the volume of the pond is truly 6000 gallons. At this level it shouldn't hurt the plants, and shouldn't interfere with the Proform C or equivalent. I agree with icu2 that the treatment of choice for us would be the Chloramine-T. With gills in this condition, I would not use the PP treatment. If your treatment with Crystal Clear Wipeout Bacterial Control is an antibiotic that sets back the filters, then it will not have a long life in the pond as it is consumed by the killing of the filter bacteria and some of the other bacteria in the pond, so don't worry about any cross contamination actions of it with the Proform C. Proform C calls for a 25% water change before each days treatment for 3 days straight. This water change does 2 things, one dilutes the unwelcome bacteria and parasites and two improves the performance of the Proform C by reducing the stuff that will neutralize it like DOC's.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard