I think you need to add larger doses of bleach at a time. In a pool your size, adding 4 gallons of 6% bleach will raise your cl to about 9.6ppm. Since your pool is so green, it is immediately being consumed killing the algae. Try adding 6 gallons of bleach. If you are home in the afternoon, test and add more bleach. As many times a day as you can test and add bleach is going to clear the pool that much faster. Regarding the low pH, Borax is what you want to add, not baking soda. Baking soda is used to raise alk. Add a box at a time slowly to the skimmer breaking up any clumps. After several hours, retest pH and redose as needed. Do NOT test your pH when your chlorine is high however because you won't get an accurate reading. Test it before you add the bleach. Continue filtering 24/7 and backwashing as the pressure rises. Also, brush the pool walls and floors. That will help the chlorine get at the algae better. It may take a lot of bleach to clean this pool up but keep hammering it! Since this is a large pool and since you have no cya, you may want to consider shocking it with dichlor for awhile as it will add chlorine and cya at the same time. You won't want to use dichlor all summer however or else your cya will get too high. If you do decide to use dichlor, monitor your pH as it is acidic and will cause pH to drop and also monitor your cya. When you get to cya around 40 or so, discontinue using any form of stabilized chlorine and stick with bleach. (Of course, if you prefer not to use dichlor, you can just use large doses of bleach now and add the cya later.) Hope this helps.