Hey, it'll be alright. Most likely you've just got some files out of order, here.
Firstly, when you went to reinstall, did you UNinstall first? Try removing all traces of FeralHeart from your computer, then reinstall. This should reset all of your files, and allow the game to play.
When this is finished and functioning, try downloading the items pack again. There should be a ReadMe file in it, which will tell you how to install the items. If not, let us know here, and we'll find you a tutorial that will show you how to download them. Good luck!