Please note my EDIT message in your post above.

Regarding the phosphates --- you got "poolstored." Selling people phosphate removers is the latest money maker for pool stores. I suggest that you not add it to your pool. Also, there is no way a pool store could discern a CYA reading of 7.

At any rate, since you have well water, that means there is a possibility of having metals in your water. So, I am going to move this thread to the metals forum where you will have more people who are familiar with this set of circumstances notice this thread.