The player must be able to view the container and take items from it, but not drop/split items to the ground from said container. 

The only way I see to do this is to use OnItemDropped and OnItemSplit hooks to create a new item from dropped item, place new item back in the container and remove the dropped item... This is tedious and not very elegant. Is there a better way?

Solved: returning non-null value with OnItemAction, this works for both split and drop