I have a breadboard similar to the one above, but twice the length. The row (or I guess column depending on how you're looking at it) doesn't complete a circuit almost like there's no metal below.
My last question is why do you recommend a 10k pot instead of a 100k.
Because that is what is recommended in the data sheet.When a channel is changed or the input voltage changes if the impedance is too high then there is not enough time to charge up the sample and hold capacitor on the front of the A/D.