To use Softlimits correctly, you really need to home the machine first, to get a reference position for the softlimits. If you home to the top of the Z axis, which is typical, then Z max=0, an Z min= some value less than 0.
Since you aren't actually running a machine, if you want to play with softlimits, you need to pay particular attention to the axis DRO's, and make sure that the position the"machine" is in would be valid. Sounds like you are jogging outside of what the actual limits should be.
Safe Z doesn't restrict movement. It's a feature to lift the spindle to a safe height to prevent the tool from hitting clamps or other things.