Yes. So, basically you have had water in the pool for 3 days now with no chlorine. Probably an algae bloom starting. Shock the pool with bleach up to a cl level of about 10 and try and hold it there. Test 2 or 3 times a day (or even more if you can for a couple of days) and each time, add enough bleach to get back to 10. Make sure you test and dose at least morning and evenings plus whenever else you can. When the water starts clearing and you are not losing more than 1ppm of cl from sundown to sunup you'll be ok and hopefully the algae will be dead. By the way, in a 15,000 gallon pool, every quart of 6% bleach will add 1ppm of cl to the water. Also, run the pump 24/7 while you are trying to clear the water.

You are right, until you get some cya in there, your chlorine is not going to stick around long. Get some cya and put it in an old sock and hang it in front of the return jet. Add enough per package directions to aim for an initial level of 30. Do NOT broadcast it around the pool like the label may tell you to do. It is slow dissolving. If you can squeeze the sock a few times a day, that seems to speed up the process.

Yes, your TA is too high. Get the algae defeated first and then you can work on that. Post with any more questions you have.