I suppose that some legal options are available to Rick Astley and other people whose name are hardly well known. But can they realistically do anything with it apart from causing another Streisand effect? Who is to blame for that, who is going to pay billions of dollars? YouTube? 4chan? Tim Berners-Lee?
The reason we're discussing porn is because that's what the article is about. The point that people should be prevented from sharing things that they don't have permission to share (unless it's in the public interest for it to be shared) is an obvious one and mostly how the law works already.
One more very important thing to remember here is that the woman in the article was the victim of a crime and the video in question is of that crime taking place. It's not 'simply' porn. It's a video of a sexual assault, and the victim is the one suffering because it's on the internet. Arguing that it should be allowed to stay on the web is arguing that the victim of a crime should continue to suffer forever. Freedom of speech, freedom of expression, etc have never covered criminal acts.
Absolutely. Swap "porn" for "credit card details" and the point I made is still true. There are some things that people don't want to be shared online and they should be in a position to stop that happening.
One individual's right to privacy is more important than another individual's freedom of expression except in very limited circumstances of the public interest. Reporting news should happen even without consent from the people the news is about because it's good for society to be able to share that information. Uploading porn or a prank video should not happen without consent from all parties.
As for your example of Rick Astley - the law already enables him to do that if he wanted to. There are many legal mechanisms for copyright holders to revoke access to their material.
There doesn't have to be one simple rule that covers everything. We're intelligent human beings. We can have a bit of nuance without society collapsing.