American Horror Story/WMG

Vivien's baby is actually the Infantata.

Jossed. Neither are.

Ben is actually Dead All Along.

To elaborate, Larry whacked him pretty hard in the basement. And we haven't seen him any where else except inside the house since then...

Jossed by the latest episode, Ben goes to the mental hospital where Vivian is confined, to see her. Unless I'm misremembering and the incident you're talking about happens at/near the end of the same episode, but the way you described it sounds like it's been at least a few episodes.
- This is old and was disproved after several episodes.

There are actually two opposing forces in the house.

One force uses the dead to try and create life, while the other uses the living to try and kill the females to keep the other force from procreating. The first force retaliates by trying to keep the males out of the house.

The "try and create life" force should be the same as the "try and kill the females" force. The house's force could be all those aborted babies, but as unborn babies, they're not very human in thinking, so let's excuse them for the unusual hell they're creating, and for being almost an Eldritch Abomination.
In "Afterbirth", Moira suggests a different interpretation. One force is comprised of ghosts who are angry and wish to inflict their fate on the living, the other is comprised of ghosts who were victims and who wish to spare the living from their fate. It's the latter group Ben and Vivien belong to, and who help run off the new owners of the house.

Violet will be the Final Girl of the first season.

In horror films, the final girl is always a young, terrorized ingenue who is somewhat savvy to what's going on around her, at least compared to the other characters. And this is especially true in Violet's case. Plus, it doesn't hurt that Violet has Tate, one of the house's spirits, on her side.

Jossed. She did not survive her overdose. Ben becomes Final Boy by default, but that only lasts for part of the season finale. His status as Sole Survivor then transfers to Hallie, the dog, who did survive.

Vivien's twins

One is a demon, and the other is Ben's, setting up a final battle between good and evil in Murder House.

Possibly Jossed, as one of the twins, Ben's, is stillborn.
- It's implied that the baby was still alive, Charles just told Ben and Vivien that it was dead so he could hand it off to Nora. It's also possible that since it died in the house, it's now a ghost baby. The finale will probably provide an answer to that.
- Yes, it's a ghost baby. Nora says it cried once, then died.

Tate didn't save Violet in time when she overdosed

And she's now a ghost in the house too. This is why she hasn't been in school for two weeks and hasn't left the house.

Confirmed during "Smoldering Children".

Tate's going to try to kill Violet

So that she will stay in the house forever with him (If Violet is still alive, that is).

To top it, Hayden will tell him to kill her.
Looks like this will happen in episode 10, based on the promo for it
Jossed. She's already dead, he just reveals it to her.

Moira will not find peace when (and if) her bones are found

After all, Chad and Patrick are still ghosts in the house, and their bodies were found. What makes Moira think she will be allowed to leave the house if her bones are found, when (and if) the gazebo is removed? Would bet on her becoming the Big Bad of the series if she finds this out (she won't be happy, in spite of her very calm and polite demeanor)

Slightly Jossed. The peace that Moira is looking for has been implied to be of the mental kind. In "Open House," she states that when her bones are eventually discovered, Constance will "pay" for what she did. All she wants is for her murderer to be brought to justice. She knows that she'll never get out of the house.

Ben and Constance will die in the season finale.

In which case the Harmons could be reunited as a family, albeit a ghostly one in the house.

It would make sense - No one can escape Murder House. Tate will most likely end up killing Constance.

More specifically, Constance will kill Ben in order to steal her grandchild and raise him up herself. I doubt that Tate will kill Constance though, given that he hates her and having to spend eternity with her in Murder House would be one of the last things he would want.
If that's the case, the 2nd season could have a new family moving into Murder House.
- A new family actually moves in not long after Ben's death. Ben and Vivien run them off. It's implied they'll keep doing it, so that nobody else has to go through what they did.
Partially Jossed: Ben was murdered, but Constance didn't die. She's still alive, three years later, and raising Tate's son.

Both of Vivien's twins survived.

Charles Montgomery lied about the first child being stillborn. Right after he says it, we see Nora being secretive. The baby we saw is actually Ben's child, and while everybody's fighting for it, the ghost baby will slip right under everyone's noses.

Partially Jossed: Nora says the baby let out one cry and then died. Vivien convinces her to return the baby.

The next season will be either in an asylum or a prison.

We have to guess where the next season will take place since the place and all the characters will change, as Ryan Murphy already said it. It was said that their was going to be some clues about where the next season will take place in the episode "Birth". In this episode, Billie Dean says about spirits: "You see it all the time in places like prisons or asylums. Negative energy feeds on trauma and pain. It draws those things to it." In the same episode, Violet talks about a prison as a metaphor, and, finally, there's a flash of someone on an electric chair. Of course, there are several other places mentionned in this episode where the second season could take place, but honestly, a prison/asylum seems the coolest.

One of the characters in Season 2 will turn out to be a grown-up Michael (Vivian's surviving twin, the anti-Christ being raised by Constance)

I know that it's going to be a completely new cast, location and story, but I can't shake the feeling that there is going to be some crossover/continuity, even if it is just a minor nod to the fact that it all takes place in the same universe. The birth of the anti-Christ is surely a pretty big deal, after all. Hard to ignore for long, one would think.