Why is my chicken all rubbery?
Rubbery chicken is normally a sign that it is overcooked.

Frying is a challenging method to cook chicken, because it is very rapid, and easy to overcook the chicken.

Some of this, you will simply learn by experience, based on the typical size of the parts you are frying, and the type of breading you use.  You will learn to recognize from the pattern of bubbles and how the breading looks when it is done.

In the mean time, if you have a quality instant read thermometer, you can take a piece out and measure its temperature.

White meat should be about 158 - 160 F, dark meat about 165 - 170 F (depending on your preference).