I was just reading about CYA this morning.
"With a SWG the odds of needing to shock the pool go down significantly, which is the main disadvantage of higher CYA levels. Meanwhile, the costs of adding chlorine go up a little (both as a capital investment in purchasing the SWG and in the cost of the cell over it's lifetime). The balance point between the advantages and disadvantages therefore shifts to higher CYA levels."
Effects of high CYA on chlorine demand
As far as these other chemicals for reducing algae, unless you are doing some procedure recommended here which requires you to drop the chlorine and an algaecide to PREVENT algae (and not ust any algaecide), they are bandaids for the real problem. I would put anything in your pool other than that recommended here on this site. You can turn you pool into a chemical stew, and the only people who benefit are the pool store people. If you think this is bad, wait until you get staining from these chemicals (such as algaecides that contain copper).
If it were me, I would probably drain it, and start over. Who knows what's in there now? Water isn't that expensive compared to all these chemicals you are using. Have your test kit ready (and one that is fresh, and hasn't been in stored the sun or heat), and set your pH, Chlorine, Calcium, and CYA. My guess, you would ready to go in a few days.
Also clean your filters for good measure.
That's what I did with multiple partial drains after buying my house. It took a while but I learned my lesson. Now I can't even believe how great the water is. It has no chorine smell, no skin drying or irritation, and is so clear, you can see almost no halo around the pool light. I now test, and add chlorine everyday, and acid as needed.