Ah Mint, Pip has a thing about crocs too and dh and I both have them as slippers and dd has them for playing in the garden. He's never actually chewed them, as we only leave them in the shoe basket in the hall, but he's cheeky enough to try a quick chomp if we sit cross-legged or even to go as far as to try and gently remove them from our feet. 
Sounds like he's had a proper teenager day, but you handled it fine. He can't growl when you tell him he can't have something he wants and if he does, he loses the privilege of being with you and the rest of the family. You wouldn't put up with one of your dcs threatening you and it's much the same thing, he's just testing his boundaries, similar to a human teenager.
The only thing I'd suggest is no collar grabbing, as that can be a bit of a trigger for some dogs. Perhaps lure with a treat or even go back to the houseline for a short time, just while he's going through his teenagery stage. Also, back to basics re leaving anything lying around that he might take an interest in, as it just avoids the confrontations in the first place. Finally, more work on 'leave' might help for when he does manage to nab something he shouldn't have.
If he's been generally unsettled that kind of backs up the hormonal/teenager thing. One thing you could try is taking him somewhere new for a walk and keep him on lead, just do a decent distance and let him get the benefit of new sights, sounds and smells. That will both wear him out and remind him that the world is bigger than he thinks, therefore perhaps he does still need you for reassurance after all. 
My two are exhausted after a new walking route today. It's been lovely and quiet this afternoon/evening.