i think first requirement for you is to have an analog output on the pin. There are multiple ways to achieve the same in PSoC. One method is to use an IDAC and a resistor. You may have to buffer the output using an opamp before taking it outside. But if you don't want to use analog components, you can always use a PWM component and adjust the duty cycle in such a way that the resultant voltage is what you want. You have to use RC Low Pass filter stage in between.
Regarding the second question, yes you can control digital output pins using control registers.