timer memory and correct level of the salt tank, Fleck Proflow SXT Downflow

Good day,
we moved into our new home four months ago, and since then we needed around 3 bags of salt. Looking inside the tank, all I can see is salty water. The level of water goes down over time, but even when no salt is left in the tank (which I can only sense through my hands), there is still at least one foot of water in the tank. My question today would be:
Should I empty the tank completely and start from scratch, filling it up with new salt? When is enough salt enough salt, up to the overflow? And should I add any water?
Secondly, down here in Southwestern Australia we have plenty of power failures. If we have one for only ten minutes, the time starts blinking after the power is back on, but not the right time, it could be any time. The service manual states it would keep the memory for up to 48 hours.
And my last question is:
The service ikon is always on, would that be normal?
Our plumber told me everything is automatically done for me, and not to worry, but I would like to understand the unit. The service manual is not very helpful.
Thanks, cheers Michael