Rafael,
I do not know how to reset all settings like you are asking.
However, I have two ideas on your z-gap issue if you are interested.
It could be a z-sensor issue.
Turn on the cubex.
Press Move on the display (for manually moving the head around or the build plate up and down).
Take a magnet and hold it under the Z-axis sensor. When the magnet gets near the sensor a "Z" should appear on the display. Move the magnet away the Z indicator goes away. If this does not work then you have a sensor issue.
To reset the Z gap without crashing (I have had this problem before).
Press Move on the display.
Manually move the build plate down closer to the bottom of the machine (do not crash into the bottom!)
Press Z-gap. The head will home and start moving the build plate up to the top.
Hold your magnet near the z-axis sensor. The machine should think it has reached Z origin and then continue to setup for setting the Z-gap.
Jog the table down a couple of inches (4 maybe 5).
Set the z-gap at this position. The amount that you traveled downward will become the new z-gap.
Now try setting the z-gap as usual. Hopefully the machine will raise the build plate up until it finds the origin, then drop it down away from the head to reach the "fake" z-gap.