Definitely interesting.
Seems like there's no rigor mortis on the bodies. Doesn't that usually start to set in after a few hours? Shelby's body toppled over, though. Still, no change of colour on Dominic. Even with a quick glance of Sidney and his employees, they seemed kinda normal. Then again, those scenes are usually dark.
Nobody ever lends money to a man with a sense of humor

I predicted on some of these threads back after episode 6 aired that we'd all be guessing what is real and what isn't because of the way Sidney had planted fake special effects all over the house. But the fact remains, if you believe the disclaimer that came on the screen about everyone who participated dying, that we are watching their deaths. I think the irony comes into play that most of the deaths we've seen haven't even been at the hands of the ghosts! Half of them have been killed by real peopleor in Shelby's case by her own hand. I think one of the many points this season is trying to make is that horror is horrorwhether it's real or imagined.

Good theory! I honestly enjoy it and could see it happening, but the thing is, why would Dominic pretend to be dead, if Shelby and Matt's deaths were real? That's the only thing that wouldn't add up.

You are right about the camera. I do not know if the camera is moving because Dominic is alive playing dead after being "killed" by Dillan. Or, if the camera is moving due to Audrey and Lee walking by Dominic's dead body.
We do see Audrey, Monet, and Rory in the kitchen discussing "Shelby acting or not acting / having real tears or fake tears / being too much or real" when Shelby first sees Matt during Return To Roanoke. Perhaps this conversation is supposed to illustrate that the actors have been instructed to act - the actors have been instructed to play certain roles during the filming of Return To Roanoke.
It may turn out that Return to Roanoke "participants" are limited to Shelby Miller, Matt Miller, and Lee Harris. Sidney intended to use horror to create a psychological "pressure cooker" that would cause the participants (Shelby, Matt, Lee) to confess to Murder One in just 3 days. Perhaps Agnes going homicidal was not planned by Sidney. However, since Sidney hoped for Agnes to break the restraining order and show up to the filming of Return To Roanoke - Sidney would have also anticipated the probability of Agnes showing up on "set" in a similar manner as when she (Agnes) was threatening the public with a cleaver(after filming MRN).
Perhaps Dillan was in Diane's backseat - thought that he would scare her for fun - the prank went wrong causing Diane to crash her vehicle. Eventually, Dillan regains consciousness - The Polks have already taken Diane's body. Dillan continues on playing PigMan unaware that his prank led to the disappearance of Diane Cross?
Perhaps Sidney did not anticipate the actions of The Polk Family.
In the end Sidney will end up with a documentary film that does capture Lee Harris confessing to the murder of Mason Harris (Sidney's goal). Sydney may be dead because he failed to correctly anticipate that Agnes would show up on set with a cleaver and murder him (along with several other people).
Or, perhaps, all of the deaths other than Matt and Shelby's may have been staged by Sidney - making Lee Harris the only participant to survive (given the word "participants" is used to describe Shelby, Matt, and Lee)? This is why Dominic's camera is moving - he is really alive after being faked killed by Dillan - however, Dominic was "thrown" by Shelby murdering Matt and killing herself. Thrown but prepared - this is why we hear Dominic say "I tried to stop you/her but there was nothing I could do" over and over again in regards to Shelby becoming both homicidal and suicidal during filming.
It is difficult to know what is true and not true. We know that Lee Harris lied throughout MRN, lied about her motivation for agreeing to be a participant in RTR. Why would Lee Harris agree to go back to Sappony? Why would Lee Harris return to such a dangerous location? A location that she claims her daughter's life was in jeopardy / her daughter, brother, sister in law, and self barely made it out alive the first time.