Centering steering wheel - how fine is it possible?

[dj92]

Hi there,
When I've had my Yaris repaired some time ago after a small accident, the steering rack had been replaced.
At first, I did not see that the steering wheel was some degrees off center, but now it is getting on my nerves.
Don't get me wrong, the steering itself works fine and does not seriously pull to a specific side (about 0,5m per 200m driven).
I just want the steering wheel to be as level as possible when I'm driving straight forward.

As they proved to be incompetent idiots ("Letting the lower engine bay cover hang down, not reattaching it? Yeah why not, not our circus, not our monkeys"), I don't want them to fix it but want to do it on my own.
(The stealership is about to lose my trust, too, but this is another story...)

I have already tried unscrewing the steering wheel, putting it out, rotating it by a tooth's angle and reattaching it, but then I have almost the same angular error in the other direction

Now I'm not sure whether I can get a higher correction precision on another place in the steering stuff.
Does anyone of you have an idea?