Why is my linear pot is causing a non-linear voltage at my ADC input?
I'm not going to attempt to read that mess but I think I know what JRE's getting at : you may have a circuit like this:







simulate this circuit &ndash; Schematic created using CircuitLab

Now with R2 at 100% the output is obviously very close to 3V3, and at 0% it is 0V.

But at 50% R2 = 50K and V = 3.3 * R2/(R1 + R2) = ... very close to 3V3

Even at 1%, R2 = 1K and V = 3.3 * R2/(R1 + R2) = 3.3 * 1000/1150 = 2.87V.

Which matches the symptoms you describe.