The wiper of the pot is what is hooked to pin 4. You are reading the resistance of the pot when you move the pedal. All pots have a section near each end of travel where the wiper goes to zero ohms to that pin, that is normal. Some photos or a better drawing would really help. What you are dealing with is a voltage divider the max amp pot is wired in series with the pedal pot, and goes to zero ohms for max amps. What you are looking for is a combination that will give you max amps at full travel, and about half amps at half travel. You do not want a log output, as that is what you have right now. You need to make the circuit more linear, in it's behavior. If you parallel a resistor across your max amp pot, you will lower the resistance. The taper will not change very much. Most pots are labeled with the taper A = log and B = linear. It looks like what you have there is a 470 kilo ohm log taper pot. A photo of how the leads are connected would help determine if the taper is wired in a way that makes it more touchy at high settings.
An no a pot never goes open, you are just not using the correct range to measure it. Yours should go from aprox 470k to 0 but I have to see exactly how the legs are wired as often when a pot it only using two leads, the wiper is shorted to one end. This makes it behave slightly different.