The unit has a 180 minute cycle time. If the percentage is set to 50%, the unit runs for 90 minutes and then it rests for 90 minutes (not generating even though the "generating" light is on).
Then, it reverses polarity and begins a new cycle. The polarity reversal helps reduce calcium carbonate scaling in the cell.
To make the box reverse polarity, move the switch to off for a minute or two and then back to auto.
The instant salinity in both polarities should be close to the same number.
Regarding the 2 ohm reading: 2 ohms is the cold reading. Once current begins flowing, the thermistor heats up and the resistance should drop. In certain failures, you might get 2 ohms cold but the connection might not be good enough to sustain actual current. I'm assuming that the thermistor probably expands when hot. When expanded, the connection might open.
If the thermistor is bad, it probably won't measure 2 ohms. If it measures 2 ohms, it's probably good.
But, I don't think that you can say that just measuring 2 ohms confirms that the thermistor is definitely good.
To confirm that the thermistor is definitely good, I think that you would need to put through at least 8 amps to prove that it will sustain the current.
To verify that the thermistor is good, you would also want to verify that the resistance drops according to the published curve.
I would refer you to the manufacturer for actual engineering data or test requirements.
Inrush Current Limiters - Thermistors | Ametherm