So, i ran the script a few times, and it DID manage to hide everything from my timeline, but it DIDN'T delete everything it could've deleted. From what i've been reading on the comment section of the script's fork, it seems that i'm not the only one having this issue, and it's probably due to the code not being up-to-date with the latest changes Facebook has implemented.
I learned that it's actually against the Facebook ToS to execute scripts on Facebook, and they've even sent a C&D letter to the suicidemachine website, which previously offered a way of committing Facebook seppuku. The Internet always finds a way, of course, and the fork was being consistently updated - the last update was only 3 months ago.
I guess i should be happy that the script managed to do as much as it did, but i'm still unhappy that it didn't delete my commenting history & my likes, which is something i'll have to do manually for now.
Still, i'm going to have MUCH less work doing it, and i can take my time doing it as well, because everything is now at least hidden from my Timeline. So now all i gotta do is clean up my photos, untag me from any photos i deem necessary, unlike any pages i don't want anyone to see i've liked, and leave my Facebook squeaky clean, not really posting anything on that PoS website that can compromise me in any way.
Facebook will stay simply as a way to keep in touch with people i otherwise don't have a lot of contact with, and that's that.