Possessiveness (Again)

I know I've made topics on this before, but still.

Loki's made some progress with being possessive. He got possessive of new toys, like when I gave him a frisbee he'd growl if I tried to take it off him. Now he's not like that, he actually understands the concept of playing with new toys and how fun it is, and rewarding, so he no longer shows any possessiveness with toys, which is brilliant.

But he still has a bit of a problem with bones and those kinds of big, tasty items. He hasn't growled in ages, his response now is to run away or try to eat it quickly, which isn't as confrontational as growling, but still not ideal. Problem is that I feel like it's a catch 22, everything I do might make it worse. If I take it off him so as not to reward his behaviour, it'll make it worse. If I trade with him and give him something better, it'll reinforce his behaviour by kind of rewarding it. I'm just not quite sure the best way to go about it. I haven't given him anything like that in a while, because while I'm unsure how to deal with it, I figured the best thing to do is to at least keep it at the same level rather than make it worse.

I was also thinking of taking his food bowl off him while he's eating it, putting some chicken or fish or whatever in it, and then giving it back to him. He won't leave his food if I tell him to, but his body language doesn't give off any indication that he's being possessive either. So not sure if it's possessiveness or greed since he doesn't growl or seem annoyed, just continues eating and ignoring me. Anyway, my thinking was that if I just take the bowl from him, only to give it back with something extra, he'll start seeing it as a good thing and it'll help with things in general. Does this seem like a good idea, or could this exacerbate the problem?

Sorry for the long post, just wanted to give as much background/info on it as possible.

Can you touch him or put your hand in his bowl while he's eating?

With bones etc you need him to respond to 'leave', then take the bone, stand up, then give it back with loads of praise.

Yeah, I can touch the bowl, him, his food, etc. without him growling or without any change in his body language (that I can see, at least). So it seems to be just high-value things like bones.