Bless you HPC for putting up with this c**p. I have seen it myself. If children behave like this at school it gets taken seriously yet the global workplace is full of it.You seem like a decent sensitive guy.

Dont leave until you have something else lined up or reduce your hours and fill the gap with another place ready to jump ship if you feel you must because why should you stay in a negative place for hours per day? You will get a ref whilst still in the current place. Tell your (poor) management that you want a change of scenery for a while or any excuse you can as to why you appear to be sliding.

Once you get to this stage start submitting grievance if you wish.

Thats the extreme scenario. I have a better idea....you can buy stainless steel food storage cannisters with clip tops, this clip can be padlocked...padlock the cookies inside it!!! They are in fact stealing and you are stopping them taking the stock. This is what I would do and Im not joking. There will be no more need for talking it out with them then. You can smirk all day! Hahahaha! plllllurrp to them!