I guess all pots have some dead band at the edges.

Good quality should be far less than the chinese ones. Also cheap chinese have other problems like linearity, differencies between pots and contact quality.

Even if you "stretch" the value from 1014 to 1023 the feel of the deadband turning the pot will be there. You understand that since you produce no values for that angle, you cannot produce also in software something from nothing!

As for the the input impedance of the ADC in general PIC have a max of 10K for reliable sampling. Using 1 or 2K pots will make shure that you are very much OK with the specs.

Ioannis