Practice your long stays somewhere else besides meal time.
I disagree with this. (As do most behaviorists)
If you are showing your dog you control the resources, you should control the resources.
The true test if the human is the leader of the pack is this one:
Does your dog sit undemanding until you free him to get his food?
In the dog world, the leader does exactly that- a subordinate dog waits until it is his turn and is allowed by the lead dog.
This isn't about practicing "long stays", it is about establishing pack order.
A happy dog knows it rank in the pack.
If the dog is barking, then the food bowl goes away and I leave the room.
To me- that is noncompliance--
For tips on teaching a quiet sit with only PRAISE---see my other posting.