So here is a question. I have an item and I want the item to do different things based on its NBT data (if this is the best way to do it). I want the player to be able to change that NBT Data with a keypress. So the default item when you create it/craft it sets up an NBT field and sets it to like 1 and when you right click puts resistance on you becasue that field is one. This will make it very simple to just use a switch to determine which ability to cast since the NBT will be an int field.  

 

The player then can press the "M" key or whatever and change the item being held's NBT data field to like 2 and this will make it so when you right click the item it will cast Fire Resistance or something to that effect. So is this method the best way to do this? Or is their a better way to do it? Plus I'm imagining packets would need to be involved so that the game knows "When player presses <KEYBIND> change the NBT Data" right? 

You need to use packets. The server doesn't know dick about keybinds and the client's NBT data gets overwitten by the server's copy.

Got it and applied it. Seems to work fine on both a server test environment and regular singleplayer environment. Found it easier to have a keybind press pass the player and their hand to a function that alters the NBT data of the item the player is holding