Regarding the max voltage of the ADC i think i have read somewhere that the max positive voltage is = to the max positive voltage reference to the ADC, if no voltage reference is specified then the max is the chip positive voltage, i guess that yours is the last option... only the more crafty chips have voltage reference inputs
In any case try tho ready on the datasheet of your Pic everything regarding the internal ADC, try to find something about the voltage references and if it is internal then you won't have to connect anything else, but you'l be limited... usually it might sufice
Regarding the PWM output, you can *try* (on the simulator first might be a good idea
) to use an bipolar transistor to drive the gate on the IR2101 !
Have fun !
P.S. : Regarding the logic you can try to find some ASM mnemonic to do the One's Complement or if using C/C++ use the "~" bitwise operator !