Song goes ~ Until 1:40 you did a great job
THAT KEY CHANGE WAS THE WORST MISTAKE EVER
Why?
It sounds awful and totally not fitting. You're trying to make an OMFG-Styled song, for whatever reason but he isn't using Moll in a Dur toned tune AS KEY CHANGE.
Sure you can use some Moll notes in a Dur Melody to make it sound more different but your base melody already was perfect.
Little tip to try out - make a drop the next time instead a key change, keep the melody going, don't make the drop too hard, make it funky and flippy. That's the style of OMFG - funky and flippy, bleeps and bloops, you get the idea?
Now to answer the question "When can I use a Key change like that at all?"
The answer is classical music including orchestra or a single instrument like a piano or smth. Because THERE you can put a key change from Dur to Moll easily to change the mood and it's way more fitting than in a song that should actually sound like some one else's song.
However. Last but not least - please don't brag about how long you took to work for a tune. Everybody starts and when they start they need long but after that they need either even longer or not. Difference is how much effort are you going to put into a track?
Because I sit here now for almost 2 months writing poetry and putting it into a video but I'm sure as hell it'll be fricking good.
16 hours are two work day (8 hours) so for people like me, putting a gigantic effort in what they do, it's honnestly nothing. I just wanna say - it's okay it feels exhausting but don't push yourself or creativity becomes fatality and you create something like you did on 1:40.
There's also a little expert tip - if you THINK you're done, sleep a night over it and take a look at your work. You'll see your work from a perspective of a viewer, not the maker and see what's good/bad in it