I liked the short. I really like the use of your switching between b/w to color as if she coming out of Plato's cave of shadows into the rest of the light spectrum. I'm guessing she shot herself at the end because she walked out of one cave right into the next one which was not what I expected. I'd like to think she was enlightened rather than ruined. I'm not sure what the moral of this was now lol. But nonetheless, it was outside of the box and very creative. I liked the use of scrathy audio as well.
On technical note, its art so
If you are shooting at an ISO 400 you dont need a ND filter just lower your ISO. An ND filter reduce the light passing through the lens. Your ISO is basically controlling sensitivity to light so you can go down to 100 or 50 if your camera allows for it. F11 does a great job at picking up detail but you have it over exposed so the details in the plate are blown out.
So place one of the plates on the wall and get the exposure right. Take a picture and see if its exposed correctly. Otherwise your did nicely. Your shutter speed is appropriate and created the blur you wanted so I'd keep that the same. Nice job.
Yeah Auto White balance is an issue because it can change. Set it based on the type of lights you are working with and you can always readjust white balance if you shoot raw. And you should be shooting RAW as it gives you the highest quality file.
Honestly I think its your f-stop. You have a wide open aperture so you depth of field is going to be shorter which will cause for out of focus backgrounds. In your last video clip you had an f11.3 which showed much more detail. Based on your description of your problem, its basically a depth of field issue. Try using this depth of field site to calulate your focal range. You need to do a little pre game planning prior to your shoot.
I had the same issue but read up on the hyperfocal distance and you'll understand what I am talking about: https://en.wikipedia.org/wiki/Hyperfocal_distance
Also, where are you focusing your camera? Infinity??
IMO, your camera is fine you just need to refine your use of it.