How the (earth) ground works?
To answer your questions, in order:

Yes and yes.
Essentially, yeah, but not quite. No this is not safe in all cases, because nothing is safe in all cases.
The wrist straps provide that path. You can indeed also ground yourself by putting one hand on a grounded pipe or something.
Lightning is complicated and I'm not confident answering this one.
The ground itself is not very conductive, and just touching it doesn't make good low-impedance electrical contact. The pole has a much larger contact area and goes down into wetter ground further underground, which is more conductive.
The earth's conductivity is extremely complicated, but basically it takes time, and quite a lot of it, for the current to &quot;spread out&quot; over the whole earth.
Think of the earth as a big capacitor.