Buy some cya. You may be able to buy it at Walmart, Lowe's or Home Depot. It may be called stabilizer or conditioner. Check the ingredient label. If is says cyanuric or isocyanuric acid, that is it. Add enough per label directions to get an initial reading of around 30. Add it to the skimmer while the pump is running. Then, don't retest, add more or backwash for a week to let it dissolve completely.

In the meantime, you're gonna have trouble keeping a chlorine reading in the pool. Probably test it morning and evening and each time add enough bleach to bring the cl back up to 5. After you start getting a cya reading, you'll be able to just test and dose it with bleach in the evenings. Your alk is fine, but you don't really want it much higher. Same with ph. We usually say 7.4-7.6 is best, but anywhere 7.2-7.8 is acceptable. If it goes any higher, you'll want to add a little muriatic acid to lower it some. Hope this helps.