Initial auto-leveling configuration
Well, I´m using marlin for my printers and normally the offset is negative, this difference is from the 0.0 Z value sensor and nozzle. 

For example, I have an aluminum plate, so this material is less inductive and I'm getting a height of nozzle 1.2 mm; normally this value should be above 5mm, but my printers reads 1.2mm

So my offset is 1.2mm (this values is dangerous for me) because I can bend the plate if sensor stop working.

the safety z height on G28 is 4mm and also for auto probing G29, the speed testing for Z is lower than travel X and Y. 

    #ifdef AUTO_BED_LEVELING_GRID

    // set the rectangle in which to probe
    #define LEFT_PROBE_BED_POSITION 8
    #define RIGHT_PROBE_BED_POSITION 156
    #define BACK_PROBE_BED_POSITION 156
    #define FRONT_PROBE_BED_POSITION 8

     // set the number of grid points per dimension
     // I wouldn't see a reason to go above 3 (=9 probing points on the bed)
    #define AUTO_BED_LEVELING_GRID_POINTS 2


  #else  // not AUTO_BED_LEVELING_GRID
    // with no grid, just probe 3 arbitrary points.  A simple cross-product
    // is used to esimate the plane of the print bed

      #define ABL_PROBE_PT_1_X 15
      #define ABL_PROBE_PT_1_Y 156
      #define ABL_PROBE_PT_2_X 15
      #define ABL_PROBE_PT_2_Y 20
      #define ABL_PROBE_PT_3_X 156
      #define ABL_PROBE_PT_3_Y 20

  #endif // AUTO_BED_LEVELING_GRID


  // these are the offsets to the probe relative to the extruder tip (Hotend - Probe)
  // X and Y offsets must be integers
  #define X_PROBE_OFFSET_FROM_EXTRUDER 0 //25
  #define Y_PROBE_OFFSET_FROM_EXTRUDER 0 //29
  #define Z_PROBE_OFFSET_FROM_EXTRUDER -1.2 //-12.35

  #define Z_RAISE_BEFORE_HOMING 4       // (in mm) Raise Z before homing (G28) for Probe Clearance.
                                        // Be sure you have this distance over your Z_MAX_POS in case

  #define XY_TRAVEL_SPEED 7000         // X and Y axis travel speed between probes, in mm/min

  #define Z_RAISE_BEFORE_PROBING 4    //How much the extruder will be raised before traveling to the first probing point.
  #define Z_RAISE_BETWEEN_PROBINGS 4  //How much the extruder will be raised when traveling from between next probing points


I hope this help to understand your settings. 

I have set the values to Zero instead 25 and 29 because I pre defined the testing points manually to 8 and 156; of course the center of the nozzle is moved 25 and 29 mm from the plate center, this avoids collision to X0 and Y0. And I just the level using 4 points once, if your bed is warped so is needed more internal points

  #define X_PROBE_OFFSET_FROM_EXTRUDER 0 //25
  #define Y_PROBE_OFFSET_FROM_EXTRUDER 0 //29