I'm going to answer your last question first. Yes, you must get a better kit especially since you have such high CYA. Take a look at the Best Guess Chlorine Chart in my signature below. You'll see that pools with high CYA have to run higher than normal chlorine levels and your kit isn't going to be able to measure high enough. Order the Taylor K2006 or 2006C (better buy) from the test kit link below. Otherwise, you won't have the capacity to measure your chlorine to the levels you are going to need.

Stay out of the pool store. They are selling you a bunch of expensive stuff you don't need. Tell your son not to add any more stuff.

Your calcium hardness and TA are REALLY high. If you don't watch it, you are going to end up with a pool that looks like milk. No more cal-hypo, calcium or baking soda!

Since you have had a chlorine level below the minimum needed based on your CYA level (per Best Guess chart), I'd suggest shocking the pool up to 25ppm in case you are on the edge of an algae bloom. In your pool, each gallon of 8.25% bleach will add just about 7ppm of chlorine. Add enough to get to 25ppm.

Order the kit ASAP. You're gonna need it.