I can't understand where the problem is, or what you call backfocus.
You focussed dead on the "focus here" text of the chart, right? Then you notice that there are more millimetric lines in acceptable focus behind the target than in front of it. Is it your point?
If yes, it is not at all a matter of backfocus or whatever, but just a very basic optical law of the depth of field:
When somethoing is in focus, the depth of field (the distance in which out-of-focus objects will appear as "in acceptable focus") is parted 1/3 in front of and 2/3 behind the focussed target.
In other words, imagine that your distance-aperture combination gives you a DoF of 3 feet when shooting your old grand aunt from 10 feet away ; everything situated 1 feet in front of her face and 2 feet behind will also appear as well focussed. This means that you'll get a perfectly focussed picture of your dear auntie, including her legendary welcoming breasts and her not less legendary huge backside.
That's what I can see from your test pictures, not more.