A CYA level of 55 is just fine. Just use the Best Guess Chlorine Chart in Janet's signature above to keep your chlorine in the proper range.

Instead of using the "slug" method to lower TA as you have been doing, please read the information at the following two links:

Lowering Alkalinity Step-by-Step

Using Muriatic Acid Safely

Also, please fill in your pool's information into our pool chart as that makes it easier for people here to help you.
Pool Chart Entry Form
Pool Chart Results
One last thing, you have given us some of your readings, but we need chlorine readings taken with a drops-based kit. Then, somebody here will try and help you.