It is difficult to dispute "9 facts" organized as "A, B, C, D".
Contracts are a legal construct of individual nations. As a foreign employee in any country, you would be mistaken to interpret your host nation's contract as being equivalent to your native country's. It is not.
I worked for a decade at six employers in four cities in four provinces in China. Five universities, three public/ two private, and one privately owned language center. I was never paid late. Not once. Additional classes were only added upon my approval and I never was assigned to work at a 'satellite' location. It is important to note that I never located or accepted a job with an agency or recruiter. I would suggest that your litany of complaints are substantially a result of agency/recruiter practices.
China has far fewer foreign teachers than it had when I first arrived. I would not call this an "exodus"; I consider it a purge. Most of my foreign teacher colleagues were incompetent. Almost all were uncredentialled. A significant portion were suffering from psychiatric difficulties and substance abuse. It is fortunate that they are no longer given classroom time with students.
I believe that the responsibility for the poor quality of foreign teachers in China falls directly on the employers, the immigration laws, and police enforcement. China has been attempting to clean up its language education industry with variable results. Foreign teachers with genuine teaching credentials that contract directly with universities in China are likely to have a positive, if challenging, opportunity to interact with students who are more respectful and more grateful than they are likely to find in Western countries. Foreign teachers should not mistake teaching in China as a career; it is not. But it can be an amazing and valuable life experience.
It was for me.