"According to PoolMath, if I add 104 Oz my FC will go from 0 to 4.0 so what am I missing?"
You are missing the whole point of what we are trying to help you do. We are trying to get your pH near 7.2/7.4 (seems to be done) and then raise your chlorine level to SLAM level and maintain that high level until the pool is clear, hopefully Friday.
Did you read what SLAM is and how it's done ?? Did you see the CYA/Chlorine chart that tells you what level FC you need to have for a CYA level of 40 ?? If you are adding bleach to hit 4 or 5 you missed something big time.
How to SLAM -->
http://www.troublefreepool.com/content/125-slam-shock-level-and-maintain-shockingl
CYA/Chlorine chart. Yes you have a SWG but I'm pretty sure I said something about turning it off during SLAM and letting the cheap bleach do the work. -->
http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock
I don't want to be critical and I did offer to walk you through this but you have to do some reading and if you don't understand read it again and ask anything that isn't clear. Without understanding you'll start loosing help and soon all you'll have left is some guy at the pool store selling you a 20 to 40 dollar bottle of "stuff" and saying try this. Next day he'll grab a different bottle and say "try this" until something works or you get frustrated and come back here and are willing to spend a litttle time to read and understand what we are trying to guide you through so
YOU understand how to do it, and what's going on. That's the only way this will work to keep your pool clean, no pool store and a bit more $$ in your pocket .
- - - Updated - - -
You need to carefully add enough bleach to hit 16ppm FC and then test often to try and MAINTAIN that level to clear up your pool.
- - - Updated - - -
Other page I explained about CYA/stabilizer that AFTER the SLAM you want to be up at 70-80 for the SWG but it's better for doing the SLAM that you are lower, takes less bleach. Look at the CYA/Chlorine chart, the more CYA you have the more bleach you need to do the exact same amount of sanitizing in your water.
You also need to take care doing the tests and try to be more accurate than 30-50 CYA if you can. Late at night with a flashlight just isn't going to cut it. Dip down and bring a sample inside and try to always take the sample from the pool with the pump having run a bit to mix and from an arms length down. Test inside under the same light each time. We already have one strike against us using strips I don't even want to think about incandescent vs fluorescent vs outside flashlight. I know you're using strips but the better the info you give us the better we can help you and the faster this goes.
Maybe it isn't the SWG getting ready to rool over and die it's the waters chemistry killing it ??? To get the SWG to perform well you need to keep it in properly balanced water. One more thing to cover AFTER the SLAM.