As for the last one. well, yeah, you're right. it doesn't explain much at all except for my love for bumping to Emily Wells (artist song in the trailer) Trailers these days have too much info in them so I wanted to keep a lot of mystery to the movie.
But there's a way to keep the mystery without confusing people and making the general plot line hard to discern. All I got from your trailer was a bombardment of unrelated and out-of-context scenes that didn't seem to have a clear through-line.
If i can say anything about the movie is: it is a Monster/sci-fy/slasher/romance/thriller/action/comedy
I understand your enthusiasm and wanting to nail down what your film is. But
Shaun of the Dead is labeled as a horror comedy. Now quite often when you think of horror, it's either a very slow moving film with a nearly helpless protagonist, or its a very bloody and gore-filled film with some action set-pieces. So Horror can imply the action. It can also imply the slasher element, and the monster element.
So horror, which you didn't even use in this list of genres, implies about four of the others. Romance is also very common in almost any film. So unless the romance is the absolute main focus and there's no action scenes or sci-fi elements involved, then you can use the genre Romance as a selling point. Otherwise, depending on what else your film stands for, you can drop that descriptor because it's not as important as stating the others.
I also don't know if sci-fi is really necessary, because unless your film takes place on another planet or in outer-space or in some sort of experimental vessel, then you shouldn't need to state the Sci-fi aspect.
Cabin in the Woods is most certainly a sci-fi, and even a fantasy film when you break it down into all of its "mysterious" elements. But to say that it's a sci-fi film likely can end up suggesting what the ending of the film will reveal. So it's best to leave sci-fi off in that sort of case.
However, it is very important to state whether your film is a "comedy" or not, because if it isn't, then the
entire film would be a lot different than if it was a comedy. The word comedy can also imply a sense of parody or exaggerated reality. So in case your film includes a lot of strange and out-of-left-field characters and elements that all band together to combat some malevolent force, then that can satisfyingly express that, especially when coupled with the film's trailer and poster. So in most cases you should state that something is a comedy if it is.
In conclusion, your film is a "Horror Comedy." Much more straight forward.
