So I understood that if the ratio of the resistors is high, up tp 100, the change on resistance of the divide resistors will be negligible and also the hysteresis will be small.
So I've changed the circuit a bit. Here is the new one:
However I have two problems, the fist is that the diode zener isn't really accurate, I'm not sure why it's like that. The second one is if it's even possible to determine the potentiometer's value in order to have 3.44V on R4 if VCC is 12.8V. That way the low threshold will be set to what I need it to be.