Regarding [1], the study itself mentions that stopping watching porn reverses the effect. In layman's terms: watch enough of it and the novelty wears off, but the sexual drive returns. Hardly a harm, it's what happens with every human activity.

[2] makes the big logic jump of assuming that someone who watches kinky porn fails to separate between fantasy and reality. It is the same line of reasoning as the disproven "videogames cause violence" paradigm and it is pushed by the same sort of people (personal hypothesis: they might be projecting). This could ironically point to a problem limited to at least some individuals failing to differentiate the two, but studies find that at the population level, a higher availability of porn correlates with lower rates of sexual assault. My personal reading is that it provides a safe outlet for sexual frustration and moderate desensitization reduces the chance that someone will, so to speak, get aroused over an exposed ankle.

On [3]... you're linking to a single data point, not a series nor a correlation; additionally, even if the correlation actually existed held, people's propension to form stable relationships is a preference, not a harm. It is also not related to minors, and it is not something that the state has any business sanctioning, much less with incarceration.