I am a beginner

I have the Sieg X2. The Cummins version. I want to make the Z-axis
as square to the table as possible and I don't know how. I want to
drill very straight holes.

I see that the head can be adjusted side by side. By loosing the big
nut in back. How do I make sure this is as straight as possible? I
have used a square and eyeballed it. How would I use a test indicator
or Dial indicator to make it more accurate?

Is it possible to adjust the squareness of the head front and back?
Is there adjustments for this?

How square front and back do the Sieg X2 mills come out of the box?
How would they compare to a quality drill press?

I have collets for the bits I need to use. But how accurate is the
standard chuck that comes with the mill?

Thanks so much for any help!