Re: Snarling & Growling over treats and food
I am going to second moving strictly to hand feeding for a while. He needs to know that food comes directly from you. I would also recommend that you walk through all doors before him. Before giving him water, praise anything he desires, I would make him sit, go into a down or do some other trick he knows. He should be working for everything.
The couch is tricky as your fiance wants him on there with you. I personally, don't think the couch is that big of a deal, as long as he doesn't jump up on it on his own accord, but gets permission first.
When you do decide to reintroduce the food bowl, I've heard that first walking by and just dropping a treat in the bowl gets the dog associating you walking by while he's eating with treats. You then, pause and drop the treat, then get lower and drop the treat, continuing in small steps until you are putting your hand in the bowl and putting in a treat, then eventually taking the bowl away and putting it back with the treat in. You want him to be excited when you are coming over as he thinks something good is happening. Eventually, he will just let you take the bowl, treat or no treat.
A similar approach with the kongs/rawhides may work better than the taking control approach. Also telling him what "to do" instead of what not to do. instead of just allow you to grab his treats, maybe you should tell him to sit, drop it, crate or couch. Get him to do something he is good at and is incompatible with chewing on the bone. Reward him for doing the positive behavior and simply pick up his bone.