Context matters. Some situations might give rise to liability and others might not, within the questions you pose, particularly the third one.
As a general rule, it is not a crime or a tort to watch or download a video of an adult nude or whose privacy has been compromised, although downloading a video might cause your electronic media to become evidence in a case against someone else, or evidence that you were also involved more culpably in the activity. Most tort liability and criminal liability relate to this kind of thing require the "publication" of infringing, criminal or tortious content by the offender (in part, because a person viewing something for the first time can't know in advance that it is problematic in many cases). Also, strictly speaking, watching something over the Internet always involves some sort of downloading, so the first two questions aren't really analytically distinct from each other. But, culpability can arise even if you didn't shoot the video yourself.
If you are part of a conspiracy that intentionally took actions to deprive someone of their privacy, or if you solicit such activity, you could have civil and/or criminal liability for the conduct, even if you didn't shoot the video yourself, as part of a civil conspiracy to engage in a privacy tort. Some statutes and ordinances have also been recently enacted to criminalize such activity (for example, one in Colorado), but I am not aware if Canada has enacted any such law recently, or interpreted any of its existing laws in this context. So, there are some scenarios in which sharing a video such as this one could give rise to liability. But, not every instance of sharing a video would amount to participation in a civil conspiracy.
For example, if two people worked together, with one taking the video and the other sharing it widely, both would probably have civil and/or criminal liability. But, if you share a Facebook post that shows up on your feed that has not yet been found to violate its terms of service, and have no other connection to the people involved in committing the privacy violation, the case that you have civil or criminal liability as some sort of co-conspirator is much weaker (which is not to say that the risk is zero).
What conduct crosses the line and what conduct does not cross the line is a subject that is not fully developed in the law.
In the U.S., Section 230 of the Communications Decency Act protects internet service providers who passively allow content to be posted on their sites and adhere to copyright takedown procedures, subject to important exceptions in the "Allow States and Victims to Fight Online Sex Trafficking Act - Stop Enabling Sex Traffickers Act" (FOSTA-SESTA) passed April 11, 2018 (which makes it possible to have liability to "knowingly assist, facilitate, or support sex trafficking"). But, if the participants in the activity are based in Canada rather than the U.S., neither Section 230 nor FOSTA-SESTA will apply, and it isn't entirely clear when the FOSTA-SESTA exception applies to particular content.
Canada might, for example, decide to follow the precedent from New Zealand of Jensen v Clark, 2 NZLR 268 (1982), which held that someone who allowed content that is tortious to be hosted at their site could have liability if they were shown to be negligent in allowing that to happen.
One of the leading academic scholars regarding this kind of litigation, Eric Goldman, a Professor of Law at Santa Clara University School of Law, has discussed this kind of litigation and studies of this kind of litigation at his (linked) blog. He has reported that victims of this kind of conduct are often victorious in civil litigation, but that, like most kinds of civil litigation, the vast majority of cases are either settled, or are resolved at the trial court level and not appealed (and thus do not establish binding legal precedents). But, there is no single legal theory that is used across the board in all cases, and the reported appellate cases have mixed outcomes involving various legal theories.