This has happened to me before, just make sure you put all the item textures to the items folder in feralheart, if it still appears black and yellow, Download the item pack once more because some of the textures might be corrupted.
You're not the only one having problems like this with those specific items.
It happened to almost everyone that downloaded the item pack. (and me too)
It's completely normal and might still happen after you reinstall the items, it's just that the pack maker didn't put the item texture in.
As for your crashing problem it may be your computer/laptop over heating or something in the FH folder got messed up.
Like Sura and Sheny said above save all of the important things you might want to keep, reinstall the game and put the things back in.