For the items, I suggest starting again and fresh. Download both the items (listed under 'Media folder sub-folders') and FH Contents (listed under 'Main FeralHeart folder sub-folders') downloads from here.
Place the items.cfg that you see in the FH Contents folder to Local Disk (C:) \\ FeralHeart and replace when asked. Once you have done that, go to Local Disk (C:) \\ FeralHeart \\ Media and delete the items folder. Once the items folder has been deleted, place the new items folder I told you to download into Local Disk (C:) \\ FeralHeart \\ Media (basically the same folder you deleted from). They are the items that FH originally provides, from patch 1.15.
Once that is done, all should be back to normal. Now we're going to install the items you're wanting to install.
First, download the items pack you're wanting to install. Second of all, move the items.cfg it provides you and place it into Local Disk (C:) \\ FeralHeart. Once you have done that, replace when asked. Then take the items folder it provides you, and place it into Local Disk (C:) \\ FeralHeart \\ Media and replace when asked.
Once you launch FeralHeart, all items should appear. If not, then I suggest providing the download you have so I can check it out myself.