Ok, I'm not sure how you are coming up with 12ppm FC using test strips. I've never seen any that read higher than 10 ppm . . . and it was impossible for most people to distinguish the 5ppm block from the 10ppm block.

BUT . . . taking your pH of 8.2 at face value . . . you need to lower it. PH levels outside the 7.0 - 8.0 range put your liner at some risk, depending on how far out you go. If you have a test strip that reads 8.2 and ALSO has an 8.6 block . . . then your pH may BE 8.2. But, if you have a test strip that only goes to 8.2 . . . than your pH may be 8.2 or 8.6, or 9.6!

So, lower your pH till it's INSIDE the minimum and maximum range of your test method.

And, order a K2006 test kit. If you are dealing with metals, you can't just 'get by' -- you'll need accurate testing.

Finally (almost!), how are you testing for metals? How do you know metals are in your pool? Do they come from your fill water? Is it well water?

Finally (really!), be careful about using United Chemical products. They have a tendency to put phosphates and/or bromides in everything they make. Your "No Mor Hydrochloric) is 80 - 85% sodium bisulfate (used by every other mfg's PH Minus) PLUS 15 - 20% mystery ingredients. Mystery ingredients from pool chemical companies will get you in trouble. I'd recommend using just plain sodium bisulfate (AKA sodium acid sulfate AKA sodium hydrogen sulfate).