That hardness is fine for bettas, it's soft water and we were concerned you might have hard water which isn't good for bettas.
Salt, ordinary salt, sodium chloride, is a mild antiseptic and when used at the right dose can help with a lot of fish ailments. If the salt you use at home contains additives such as iodine you need pure salt - aquarium salt, kosher salt etc.
Epsom salt is magnesium sulphate and this is used in a bath outside the tank for drawing fluid from a fish's body when a fish has dropsy and it's body is swollen. It doesn't usually work though as by the time the fish shows dropsy symptoms it is too late to save it.