Don't mess with anything yet.
Look closely at the first target picture. What I see is that the lens (at least at this distance and zoom) has a noticeably spherical focal plane (i.e. it's not flat--not by a long shot). The stuff that's in focus isn't along a straight horizontal line; it's in more of a rainbow. If you were to take a shot of a flat sheet of print straight on at these same lens settings, the edges of the image will be backfocused by quite a bit. This isn't unusual for a zoom at close distance but in a micro/macro lens, it'd be a big minus. I bet though, at 10+ feet or so and mid-range zoom, it's pretty well behaved. Secondly, the focus at the center of the target images is pretty close, at least at this distance. Close enough.
Unless you routinely use this lens at these extreme settings, I'd set up a target that is more closely geared towards your routine use--zoom-wise and distance wise.
Welcome to the world of lenses and the odd things they do.
ETA:
Also, on the focus brackets: those are just etched boxes that give you a rough idea of where the actual focus points are. Draw a small box (1/8" square or so) on a blank sheet of paper and slowly drive it into the focus brackets from different directions until the AF actuates--with a Nikon, the focus brackets appear like
[ ]
When actually, the focus points are a
+
somewhere inside the etched [ ]
