I would not use the tabs right now, just bleach.

What i wrote above:
"Each jug of 8.25% bleach will add 3.4ppm of chlorine. For now while you are cleaning up your pool and until we know your CYA reading, I'd probably aim for keeping the chlorine between 12-15. Also, run your pump 24/7 while you are working to clear it and turn your SWCG off.'

So, you test, then add however much bleach you need based on that info above, to get your chlorine level back up between 12-15. Once we know your CYA level, we may revise that recommendation but for now it will give you a target.

The yellow chlorine test is called an OTO test. If you click on the following link, it will take you to a chart that gives interpretations of colors that are higher than that kit can actually measure. But, you can use the colors to get an estimate of what your chlorine level is. When you are trying to clean up a swampy pool, you want to keep the chlorine in the very dark yellow/orangish range. http://pool9.net/oto-chart/

(By the way, when your chlorine level is over 5ppm, the pH test on that kit will give you a falsely high reading. So, test pH whenever the chlorine is lower than 5.)

Not sure about the sand on the seats. What size is your sand filter (how many lbs. of sand does it hold.) Sounds like your filter may not be working properly. To test it, buy the smallest bag of DE that you can find, throw a handful into the skimmer and watch the returns. If you see white powder shooting out, your filter is not working. If it doesn't shoot out, the DE may actually help your filter to filter better. More about that here: http://pool9.net/de-test/

Hope this helps.