My filter feeding shrimp on occasion needs supplementation and I get his food to him with a long turkey baster and I mix up the food with tank water suck it up and squirt it in front of him. I don't feed the other fish at the time since extra food swirls in to the water current and is eaten by the others. If you are using more chunky foods this may be the opposite.
I would make a crab cave in his favorite corner and cover just enough to get him get in but a rock type cover to keep the fish from coming right down to it. Make it so you can see him all the time from the side of the tank but protect him and his food from the "hog" fish!