Hi BRM,
good advice you've gotten so far. Trust these guys and you'll be golden.
Nothing is gonna harm your pool, and even if someone falls in it, they chemical levels will not harm them.
I would like to add a couple of things.
First, and most important. Relax and don't freak out. Its all gonna be ok.
Next. CYA... after you have hung your sock in front of a return in the pool, with enough CYA in it to get your reading up to 30, dont worry about testing it anymore until after the SLAM is over. Granular CYA sometimes takes a few days to actually show up in the test. Dont wait for it to show up on the test before you start the SLAM. Just consider your CYA to be 30, and SLAM it.
Next. The SLAM is a process. Your pool will not clear up overnight. Its not magic. It took a while for your water to get nasty, and it will take a while to clear it up.
Next.
MAINTAIN the SLAM FC level. That means testing several times a day and adding chlorine to bring it back up. The more you stay on top of it and keep your FC at SLAM level, the quicker it will go. We all have lives and know its hard to dedicate time, but do your best and dont give up.
Next. Brush the entire surface of your pool daily during the SLAM. Algae and other nasties, grows a bio film on it as a means of self defense. You need to brush and break up that bio film so the chlorine can attack and kill it faster. Get the kids to help! Brush brush brush! Every Day!
Next. Dont give up! It takes patience, and you will succeed!
Next. If you havent figured out how to use your vacuum yet, then you need to. There are lots of videos on YouTube about how to prime and use a pool vacuum. A vacuum will go a long way in getting the water cleared up quicker than without one.
Next. Dont worry about testing for CC until your water is clear. It will be a waste of test regents, so just by pass it until later, and keep testing only for FC. When your water gets clearer and clearer, you'll find you have to use less and less chlorine to maintain FC. When the water is pefectly clear - not a little be clear, and not almost clear - Perfectly Clear, then test for CC's and do the OCLT. Dont know what OCLT is? See my next tip.
Next. In your down time between chlorine additions, Read This. Over and Over and watch the video. YES! There IS a video!
Pool School - SLAM - Shock Level And Maintain
With the help of the forum and the slam instructions and perseverence, you will easily achieve crystal clear water.
Good Luck