I agree with Puppy. Best move would have been not to give it to him until he was ready to move in. But since you already have, give him the trust and chance that you are hoping will work. If it works, he keeps the key. If it doesn't, you can try a different approach. I think DBing is partially trying to do what works, seeing your results (or lack of) and then adjusting what you're doing. You did that (giving the key) in a positive mode, if he responds well, then good. If he hangs around with OW and does more cake-eating, then you will have to do what you need to do.
