Sorry for the late reply, it was about 11PM for me, and I was tired as hell after being at it for 10+ hours that day.
Ultimately, I figured it out with Dss0's instructions. I indeed got the file structure and the referencepoint for the FastDL URL wrong. Once I figured out how to actually get these right, It worked!
I still encountered some problems when I tried it on interserver though. When it starts downloading it just downloads about half of the files, and then just cuts off both the download process, and the game.
My solution now is just running my webserver locally on XAMP like Matrix said at the beginning, this works like a charm.
Thank you all for helping me out! Really appreciate the support!