Use
PoolMath to start by aiming by a 40ppm CYA mark. Then see what your FC drop is per day. If you're adding more than 2ish ppm of chlorine per day then bump your cya up to 50. Just depends on your pool. Keep in mind
PoolMath isn't telling you what to put into your pool to make it stay clear. It's just telling you what you need to do to meet the "goals" YOU set.
You can add the chlorine and the CYA at the same time. I wouldn't wait until you get your TA where you want it....go ahead and start now. All the baking soda is mixed up, so there's no chance of any chemical reaction.
Steps I'd suggest tonight.......
1. Add 40PPM CYA (use
PoolMath to figure out how much you need to add)
2. Add 3PPM Chlorine
3. Do a full set of tests (minus CYA) tomorrow and repost your results. We'll help you out more then.
The CYA test can take up to a week before the results can be 100% trusted. After you add the CYA, wait a week before retesting. Assume however you have the 40PPM after all the CYA is dissolved, usually takes about 12 hours or so. Having any CYA in your water is better than zero CYA, so the sooner you can get the CYA and Chlorine in there the better.