The container of CYA will have dosing instructions on it. You're looking for 30 - 50 ppm, so calculate the amount you need for your pool volume from the instructions.

From your test results I gather you're using a 25 ml water sample. You don't need that much. You can use 10 ml, one heaping dipper of DPD powder, then count the drops until the solution goes clear and multiply by 0.5. The resulting number is your FF and, subsequently, your CC value.

What is your goal with the addition of muriatic acid? Are you trying to lower your TA or your pH? This link http://www.poolforum.com/pf2/showthread.php?13111 may be helpful.