Salt treament for Ich is best at 3ppt of salt, which is 1 tablespoon per gallon. I like to spread the total dosage over the course of 3 days, starting at 1 tsp per gallon on the first day, increasing to additional 1tsp per gallon on the 3rd day, and finally one last dosage of 1 tsp per gallon on the 3rd day, which would bring me to 1 tbs per gallon total. Salinity is maintained for 10+days, adding back in any salt removed during a regular water change.
You should vacuum the bottom every day to remove the ich cysts.