Bloody hell, you're making it complicated for some user input knobs :-)

But to answer you question,yes. The datasheet has the answers, one part MAY differ from another so best to check but using the 25K22 as an example VRef- van range from 0.3 below Vss uo whatever voltage is applied to VRef+ which in turn can range Vdd/2 to Vss+0.3V.

Using voltage dividers for VRef provides a high(ish) impedance voltage source at the VRef inputs, which will be suspectable to noise. 20mV noise on any of the Vref pins is the same as 20mV noise on the ADC input pin (about 4 counts @5V).

I think we've been over this but I might have missed something....
Sample the input 16 times, sum all values and divide by 4. Now you have a somewhat filtered 12bit result. Use this value to apply offset and gain formula to get the final value to what you want. For example, lets say the 12bit value ranges from 17 to 3996.

Code:
Value = Value - 17   ' Value is now 0-3979
If value > 32000 then Value = 0    ' Make sure to not underflow in case start value is <17
Value = Value **16850   ' Value is now 0-1023