I mean this nicely - if you're resorting to hitting him - even not hard - it's time to find him a home.....he's only going to become fearful and that's never the way to train a dog.
I don't know why some get food agressive but years ago saw my husbands SWEET Cockers growl when they had their first real bone ...they just talked to each other acting all Clint Eastwood and all - but it WAS rib eye
If you're having so many issues he may need to be in a one dog home and good luck. I feel sorry for him and maybe he's overwhelmed with the new additions ?