The point of a drop checker is that you are eliminating the guesswork of messing with your ACTUAL ph/kh. You are using the controlled KH of the Drop checker. The co2 lowers the PH in the drop checker and you get a direct reading. In your tank, testing the params is basically worthless. In the drop checker you get a controlled result.
Yellow is likely 30-40 ppm. Not 70. Maybe even under 30.
Ranges of yellow are hard to read. If you ahve livestock and they are not gasping, leave it alone. The real importance of dc's is that they help you know when it is way low. They react so slowly that your fish will tell you if you have a problem long before the dc will.