I'm no lawyer. This is uneducated opinion.
btw remixing the song, without licensing it, might not be covered by fair use, depending on... things. If you want to be safe when it comes to all this, get a license. Game music is usually fine to remix (probably not ok to sell the remix), but commercially released music is different.
1. Purpose and character of the use
The first factor is "the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes." To justify the use as fair, one must demonstrate how it either advances knowledge or the progress of the arts through the addition of something new.
Quoth Wikipedia. It's transformative, in that it's not the original audio of neither the trailers nor the original song. And your own cut of the video material. Can't say if that's enough, but I would think so. Educational purpose though? Nope. But it might "advance ... the progress of the arts" though.
2. Nature of the copyrighted work
Fact vs. fiction, ideas vs. expression. This kind of stuff. You're not copying an idea, you're copying the expression itself, the video material, but re-cut. The material is fiction. The material is published. What else might matter?
3. Amount and substantiality
You're presumably using a lot of the material you can find. A trailer itself is not the whole game, but it is a complete video that's been cut, mixed, released.
4. Effect upon work's value
The fourth factor measures the effect that the allegedly infringing use has had on the copyright owner's ability to exploit his original work.
In this case, a positive effect, if any, on the trailer. Maybe also on the song.
So as far as I, non-lawyer, can tell: You're probably OK on the first and fourth factor, maybe not on the middle two. All are supposed to be considered.