By chance do you have a github or skype/discord? And do the Items exist in the game?
*Edit you don't have @EventHandler above your load and postLoad methods.
Cool alias has a sgood tutorial for overriding shift clicking here.
http://www.minecraftforum.net/forums/mapping-and-modding/mapping-and-modding-tutorials/1571051-custom-container-how-to-properly-override-shift