Orka:
Go with your numbers. A kid with test strips is a waste of time. Also, chlorine levels CAN change as the water sits in a jar. All you will do by questioning the validity of the store's test is alienate them. It's like trying to teach a pig to sing--you waste your time and only annoy the pig.

Trust your Tot Alk and LEAVE IT!

Since you have very low CYA, your FC of 3 is FINE--I don't believe you have any CC. When CYA is higher, check the Best Guess table for the ideal FC levels.


When you raise your pH with Borax, T/A will rise too--they move together.

Your plan on CYA is good--I suspect 4 lbs after it's dissolved in (takes 48 hours to a week) will be plenty.