And your point 1 is why those jobs don't like to hire people with advanced degrees, because they know you're only temporary until those people find something better. Why would many employers hire someone who might leave within a few months, when they can hire a teenager or an adult with no formal education who would probably stick around longer. I have a real life case of a friend who studied at the University of Tokyo, left with a doctorate in computational mechanics, who couldn't get any of the above jobs (although he tried), or even simple entry level programming jobs because he was told he's over qualified.
2. I wasn't talking about other countries, I'm speaking mainly of North America. The friend above is now a math and physics professor at a junior college, after being passed up on at Rice University for a tenure track position. He lost the position to a minority, even though he was also one. Just not the right kind of minority. Now he's under the poverty line in California, and certainly underemployed, although he teaches at several different junior colleges. At any rate, he took what was avaliable, and junior colleges are always looking for more lecturers in the sciences or mathematics. Unless you're absolutely garbage here in the US, long term unemployment is more of a choice than an external circumstance.
3. Maybe many are, there are also many who're full time staff, and still more who're just lecturers who bounce between schools trying to earn enough to live.