Not fired in the American sense (you can't let someone go in any short term in most European countries). She let him know that he should look for another job, meanwhile he's still employed but unmotivated.
But the point here is that he is not "unmotivated" to do his regular job (she makes no mention of that), he just doesn't want to do the free extra time on night and week end for which he was never paid with to begin with, but used to do out of "volunteering" (her own words).
You can't fire a guy and then expect him to be 100% motivated, but you can even less expect him to keep doing the little extra on the side just for you ...
Entirely depends on which country within Europe, France for example has employment laws which are incredibly favorable to employees rather than employers.
The story happened in Belgium, and the specific duration in this case would be three months, unless there are some specific details that we are not aware of. I agree that it would have been different in another country.
That depends. New hires go through a probation period up to 4 months renewable (almost always renewed in practice) were you can be fired in a couple days without justification.