If the pH is high (let me guess 8.2-8.4?) due to the additon of baking soda, water changes will lower it.
As for the fish, you know that a salt dip isn't going to completely cure the ich, right?

You need something consistantly in the water to do that, so you can kill off those little nasties as they fall off the fish and the new bugs hatch out. You can use salt for this (1 tablespoon per gal) or you can use a commercial ich med. Don't use both at the same time.
Good luck.