Try some real world tests, not the sheet of paper.
The biggest problem with that test is the camera doesn't really know where you want it focused. It might be in perfect focus, for where it believes you want it to be.
For a back focus test I'd try setting a pen, or something like that on a cup, at a bit of an angle, then shooting it.
Sorry for the very bad pic, but more or less like this.
Please do yourself a favor, and use a tripod, unlike what I did.
The whole idea of this test is the camera usually focuses on what's closest, so it'll hopefully be the end of the pencil.
It's easy to look for a backfocus issue there, by seeing if it's sharper on the end of the eraser, or beyond. There are enough marks there to give you a good idea if it's past that.
I don't know of any good methods to test front focus