Lawrence, you are your own harshest critic. You don't post many of your macro shots, but the ones I have seen are pretty good.
I think you may be putting too much pressure on yourself . I remember when I was still trying to do my 52 thread, I felt like I was stressing out trying to get shots of something that wasn't in front of me. In the end I just stopped doing the 52 thread as I felt it was taking the enjoyment out of it for me.
I get enjoyment from my macro shots, because I get home from a long stressful day at work, I can just pick up my camera and go out in the backyard and take some shots with no pressure on me, some days I get a handful of good shots, some days I delete them all, doesn't matter it de-stresses me from work.
Getting back to the sharp shot thing, I find I get my sharpest shots when I can brace my camera and hand/arm against a tree or something to stop the movement, or if you can grip the tip of the leaf with your left hand and also cup the lens in the palm of your hand at the same time, takes some practice and the insect doesn't always like it, but sometimes it will give you the shot.
I think the D7100's high pixel density sensor is very susceptible to the slightest movement. 1/200 or 1/320 is not fast enough to stop the movement at this close range, and a tripod is not practical.