OK well dogs don't think like people, putting him in the kennel for punishment isn't accomplishing anything at all. How old is the pit mix, often this becomes an issue at maturity. Pit bulls take very little encouragement to start a scuffle, they think a fight is great fun and the answer to just about any trigger, resources, over excitement and some are flat out dog aggressive but often not to all dogs. You have two same sex terriers who it sounds like don't get along great, which is not super shocking. You can try heavily managing the situation, no people food out, put one or both of the dogs up when you do but don't be surprised if it starts tilting over to other circumstances, ie just because the food bowl hasn't been an issue yet doesn't mean it won't become one. It may turn to aggression towards your other dogs as well. You need to really watch body language and how the dogs are interacting, intervene if you see anything inappropriate.
Most of us with multiple dogs never have resources out for free game, too easy to become a trigger for guarding and fights. Usually once fighting starts between dogs we recommend crate and rotate for safety, you can't force dogs to get along and better to keep everyone safe, happy and separate then let someone get injured, especially when you are looking at such a size/age difference. Getting a knowledgeable trainer involved might help but choose carefully, they aren't created equal.
These sites have some good info on multi dog homes as well.