ADCON2 = %10000000 ' ...and right justify result
how many times do we see this totally wrong statement

ADCON2 = %10000000 ' ...and right justify result and set the conversion clock to fosc/2
which is way out of limits for a 48mhz osc and contradicts the define
Define ADC_CLOCK 3 ' Set clock source (3=rc)
why not just
ADCON2.7=1
or
ADCON2 = ADCON2 | %10000000 ' ...and right justify result


other than that i have nothing , never tried a 12 bit adc chip.
you may need to do it manually