Problem with focus on new canon EOS 650D?

Hello everyone!

Here I am again with more technical questions!!!! BUT... I do love this camera!

So, long story short... First camera had a spot on my sensor that I couldn't clean (even with wet methods). Present camera has no such issues, but from the begging I though images were not that sharp! I thought I was going crazy (which is probably true), but this feeling never abandoned me!

I decided to try some more "accurate" tests (http://focustestchart.com/chart.html).

Well, it turns out I think I have a focusing problem and the AF is not really focusing sharply in the centre.
Here are a few examples of what I am saying:



Here are 4 photos, under the exact same conditions. The chart is at 45º, camera is set to middle AF point, maximum aperture.

What do you guys think? Is there anything I can do to remedy this? Should I just ask for new camera (I got it from Amazon)?

Also, are there other ways to evaluate the focus that can be more accurate?

Thank you all for you time and help!