Did you test for salt before adding the 4 bags of salt? Every time you add liquid chlorine to the pool you add salt too, so I'm guessing you already had a significant amount of salt in the water already. Did your regular additions of chlorine increase your FC by the expected amount? Your volume might really be closer to 10K as you originally thought.
I also expected the SWG to turn off when the pump was turned off. Another one of the quirks of the Intelliconnect. I have learned to just check and make sure the SWG output lights are off to verify that it's no longer working whenever I turn off the pump. It's also easy to turn off the CB for the SWG too, just to be sure.