Just some thought and questions

I use to get algae in my pool on a regular bases. Then I read about the issue with High Cyanuric acid and sure enough my reading was 150. I solved the problem by diverting my gutter spout into my pool so when it rained the rain water would go into the pool, then I used my pool pump to drain water from the pool. It diluted it enough bring the cyanuric acid down to 50. I use liquid chlorine now and very infrequently use tabs. About 8 years ago I bought a solar cover to keep the water from evaporating. It also cut my chlorine use down by 1/2 to about 1 gallon a week for a 18,000 gal pool.
Here is the interesting thing I cannot figure out after doing a lot of reading. My solar pool cover is on a reel and I keep in on the pool unless we are swimming or the water gets over 92 F. A small amount of water gets on the cover and when it evaporates it leave a white salt like residue on the edge of the cover, then when I remover the cover in goes back into the water. It build up a lot a few times and I brushed it off on to the pool deck. In live in Southern Ca so it get quite warm fast. In the last 2 years, my Chlorine use has dropped to about 1/4 gal a week. I find I add about 1/4- 1/2 gal of acid every 2 weeks to keep the PH at 7.5. Everyone comments how sparkling clear the water is and how warm it is about 90 F. The chlorine is about 2-3. The water taste slightly salty. I have not had any algae in the pool for the past 2 years. I recently had the water tested at the pool store where I buy my chlorine. Chlorine was 2. , PH 7.6 alkalinity 90, hardness 700, Cyanuric acid at 60. Phosphates was high at 1000 but he said since I don't have any algae , don't worry about it. My question is Is my pool turning into a salt water pool. Is that why I am not getting any algae and using so little chlorine. My neighbor uses about 1-2 gal a week and has trouble with algae all the time. Next week I am buying a salt water test kit on Amazon to check it. I have a Taylor 2005 kit. Thanks, I have not had anyone at the pool store able to give me any ideas.