u/Frogsknecht - originally from r/GenZhou
For the first source, from the limited bit you can read without paying (an internal contradiction in capitalism: its desire for profit drives it to censor its own propaganda) it would seem like the director wasn’t arrested for his Marxist activities. I can’t find any official police statement, but the official reason given by the University itself the next day was:

[The group] severely deviated from the promise of the instructor and leader when registering at the beginning of the semester, refused to accept the guidance [of upper school bodies], refused to submit the Marxist Club membership information, and [the leader] has repeatedly held activities in violation of regulations and has seriously neglected his duty.

Otherwise, he was released by police the same day with an administrative warning. Schools in China have very strict organization, and attempting to undermine this is taken pretty seriously.

Afterwards being released, he went back to the university and made a film claiming he was beaten, tortured, and forced to listen to Xi Jinping’s 2017 new year speech (for some reason). Like 12 students protested but it pretty much got ignored until the police made them leave the university. They got expelled afterwards I’m pretty sure.

For the second and third articles, they are referring to the conflict between Jasic Technology corporation and their workers in a Shenzen factory. The workers were mad after one of them had been fired, so the CPC union sent them a letter advising the formation of a union. The union was formed, and in the course of its strike and protests, some members were arrested by police for “picking quarrels and starting trouble” (in other words, they were doing dumb things that weren’t helping the strike).

This prompted a letter demanding their release, written by a student and worker named Yue Xin. The letter was promptly deleted for libel after the Christie Technology company complained about the truthfullness of the claims made, and they were determined to be malicious and slanderous by the Shenzen Public Security Bureau. This prompted some ostensibly leftist student groups to protest, which was quickly picked up by the British billionaire-funded NGO Amnesty International.

The story about workers supposedly being kidnapped was first broken by the Chinese branch of Voice of America, the American Congress-owned media group, whom Yue Xin agreed to do an interview with. Make of that what you will.

You can read into the second one more if you search up the Jasic Incident. I wouldn’t worry too much, from what it sounds like workers made a union, some younger members got arrested for acting disorderly, and some people protested the arrest with help from American and British propaganda outlets like Voice of America, Radio Free Asia, BBC, Amnesty International, etc.