How to make a command give you an item from a gui?

I'm trying to make a mod that makes it easier for my friends and i to get better at pvp, the idea is I have 10 "preset" blocks and in each of them there is 9 hotbar slots, 4 armor slots, and one offhand slot, so you put in items that match the loadout that you want and type in a command and it matches the preset for each player...

But whenever I type in the command it says "an unexpected error occurred while trying to process that command" I've narrowed it down to  part of the procedure...

I can't tell why the command wouldnt work, maybe it has something to do with it not being able to take out the item from the gui, can someone here help me?

(also, I made it so the preset block saves it's coordinates whenever it's placed, if that means anything)