First, complete the usual first-layer calibration and test to ensure you get adhesion of the first layer.
Second, get the test patch .stl (or .gcode) from https://www.thingiverse.com/thing:3008633. Not using 0.2mm first layer height? Not a problem... just use the Customizer (or tweak the openSCAD file) to create a .stl with the correct height. Or if your slicer can do it, scale the Z-axis only in your slicer
Third (unless you the provided .gcode works for you), set your slicer's first-layer height to match the .stl file and slice it using 0 perimeters and 0-degree infill.
Fourth, fill in the top part of the form with your current settings;
Finally, enter the recommended bed level corrections (and optionally the Live adjust Z) values into your machine. Give it another try and see if the patches come out more even.
Your goal in setting the bed level correction is to make the heights of the patches equal; they will very likely always measure a little more than the nominal first-layer thickness. Unless you are seeing poor first-layer adhesion or all patches are more than 10% greater than the nominal first-layer height, consider ignoring the suggested Live Adjust Z value.
If your extrusion is set correctly, the printer should be extruding enough material to fill the first layer, and it can only go up (and a little bit out), not down into the bed. If you set Live adjust Z too low, the filament will just make ridges alongside the nozzle and you'll be measuring the tops of these ridges which are thicker than your actual gap! Eventually, your nozzle would hit the buildplate and you don't want that.
Oh, and please do contact me or comment if you have suggestions for improvement.