Oh my gosh, you are doing a Terrific, Magnificent, Stupendous, and Spectacular job with him! I'm in awe.
We went through the resource guarding thing with Momo. After 8 years of struggling I finally got help and it was a completely different feeding routine after that. My advice to everyone I meet now is, "get help immediately, don't wait and waste the best years with your pup." From now on my dogs get the "hey, look at me," treatment at the bowl and they get a tasty addition to their bowl if they give me the attention. I reinforce it a few times per month and can take anything from them (unless they're parading around the yard triumphantly in a game of "Keep Away." Esther . . .. Gerts does it rarely, but sometimes with 5 or 6 birds of prey flying over our yard there are unexpected treats hiding.
Anyway, you're not alone in resource guarding and that video made me smile and laugh. Good boy, Finn!