I don't think you should do the salt, it may stress the fish out and make them more susceptible to the ich attaching to them. I would just use the heat to kill them off. And daily vacuum/wc. As far as the snail, I would take him out and put him in a container of tank water and return the little hitch hiker to the store where you bought the plants. Depending on the type of snail they can lay dozens of eggs and take your tank over..if you don't mind keep him/her Post a pic, maybe someone can tell you what kind it is.