it would take 3-5 grams of anti-caking agent (sodium aluminosilicate) per LITER of water before it would kill your fish. i'd imagine you would have to use pounds and pounds of table salt before you reached that level. i'm really not even sure you'd have any water left at that point, just salt paste. not only that, but it's not even soluble in water. it just falls down to the bottom of the tank and sits there.
Salt and inverts: I've never had red ramshorns and pond snails die off when using salt. If they did, there would be far fewer posts about pesty snails that people can't get rid of. I haven't and would never do a salt treatment with apple snails in my tank. I don't know about shrimp... never did it.