Yes, the muriatic will lower pH -- don't use too much! Your pool is fair-sized, but with the low alkalinity, it won't require lots. I'd try using roughly 1/4 of a gallon bottle at a time, and then testing after circulating for 4 hours. Keep the bottles out of the sun -- it destroys the plastic. A good way to store those bottles is inside a 30 gallon plastic garbage can with a lid. Be sure to read this thread on using muriatic acid safely!

By the way, keep the pH low is just to prevent the metals from staining anything. My guess is, the pool store test results are bogus. But until we know that, better safe than sorry -- removing stains is a pain!

Lemme know when you get some test results -- bucket or K2006. And, maintain good chlorine levels!