After watching Piggy Piggy it seems that a lot of these theories have been confirmed.
I am wondering now if Violet is the only member of the Harmon family that is alive and is a medium, but isn't fully aware of her gift?
I think we will find out about the rubber suit man in next weeks episode (on the 23rd). It's titled Rubber Man.I believe it's all due to the house. There's something weird about that place that keeps the spirits there... Or is it someone, and entity? Maybe the rubber suit man has something to do with that, since his story had no explanation until now. I really want to see more of him, tough.
I thought the same thing at first, but then I thought about Hayden being buried in the backyard, and she was only able to come back on Halloween. I think that if you don't have any unfinished business or something of that nature you can move on and are not a "prisoner" of the house. I do think your theory on Tate is interesting though.She wouldn’t cross-over if she died in the house. That’s like a “house-rule” as I like to refer to it. She would become a ghost. I sense there is a possibility of crossing-over at somepoint, but the rule so far is that you die and become a ghost. Except for Constance’s husband- at least to our knowledge. Maybe if you’re buried off the grounds you can potentialy move on- I’m sure Tate is buried away from the house, so he CAN move on as Constance suggests, he just hasn’t. This also explains why Moira can’t.