Do you like doing stuff by ear? Or from creative imagination? And are on a tight deadline?
Yeah, then forget about trying to learn the music theory in 2 weeks, it won’t work out. Classic a-b-a-c ton.-dom.-subdom. song in minor will sound like a kindergarden version of trying to be as sad as a silly cartoon for 3-year-olds can get.
My Idea would be: just listen to a shitload of good songs that are roughly into the direction of style you’re looking for. Watch for parts, sounds, and atmospheres that seem to fit. Then put everything into that strange blender in your head, push the start button, forget about the exact originals, and nail down your own custom spiced version of it “by ear”. From material you already got, or sample cds or whatever.
If you are gifted with a little spontaneous creativity of your own & enough experience in tracking from driving your own styles in other categories of music, this might work out alright, and even without the result being even close to a rip-off of your model songs.
Had to rise an eyebrow at the image of having…this video and then the cheesiest artificially-sad tune ever possible to remember the dead-too-soon ones? Well, try to give them dignity and respect also. Just as a hint, or else it might just seem clumsy or too alienating to some.
Also sometimes very simplistic stuff might suffice to enhance a mood in a setting and visaul images. No need for full orchestra. Minimal with single notes, very easy and subtle rhythm section, and in a simple scale with right timbre (i.e. dark timbre instrument, maybe at times audibly detuned as modulation to emphasise the uneasy feelings) and right sound design (i.e. subtle wind like elements, heavy but damp reverb that won’t swallow stuff on certain elements) can very well work if the visual image interlock in the right way to create the overall emotional picture.