FC + CC = TC. So, something isn't right with your chlorine readings. And I know you can't possibly have a CC reading of 15.3. Try those tests again.

Keep adding the Borax. Most kits won't register a pH reading below 6.8 so if you get a reading of 6.8 it could be MUCH lower than that in reality. PH below 7.0 is acidic and can damage your pool so it is CRITICAL that you get that pH up ASAP! Go ahead and add 3/4 of a box of Borax at a time until the pH starts to move and then go with smaller additions. After you add some, wait about 2-3 hours and then retest and redose. Don't put this off or you could damage your pool. Do it ASAP. (Meaning --- now, not this evening!)