How do you turn off cravings?

You can try to work it into your deficit. Or go over for a day. Like, I sometimes crave a bag of crisps. And when I do get one I won't have a proper dinner because I'd otherwise go over my calories. So it's not meant as a punishment of sorts but my craving for crisps has gone down, because having them means I can't have too much other food and might go hungry.

An option some people here have used that you didn't mention: Schedule the craved food for a future time, later in the week maybe. (Maybe cut a few extra calories in the days between to budget for a bit extra eating that day.) If you still crave it then, eat a moderate portion.

I usually did something like that, or simply got a very small amount of the craved thing, ate it, and fit it in. Usually the first few mouthfuls of the thing are the most satisfying anyway. (I get that the minimum order of KFC is still fairly caloric. Throwing away food is not an ideal thing for various reasons, but in my case I figure pasting inches on my hips isn't great, either, so sometimes I eat only part of a thing.)

About powerlessness: You know without anyone telling you that in reality you have complete control over what you put in your mouth, chew, and swallow. Yes, it can be hard to exercise that control.

We feel powerful when we successfully use the powers we have. Someone here once compared changing one's eating habits to training a puppy: The more frequently a person gives in to the puppy and doesn't require them to do what's desired, the worse-trained and more pester-y that puppy is going to be. Consistency in requiring the desired behavior eventually breaks the cycle. In other words, ignoring a craving gets easier every time a person does it: It's a skill we practice.

I'm not a fan of permanent complete self-denial of treat foods. I think it's important to manage the frequency and portion sizes. Figuring out how to do that is hard, but it is somewhat like that puppy-training scenario: We need to make a plan of what we're going to do, and stick with it.

My suggestion, if sticking with it doesn't work, is to re-analyze the plan: What were the triggers that made things go sideways? (Social situation, habit, boredom, emotions, etc.) What other ways could the trigger situation be handled - non-food ways, ideally. Spend only a few minutes thinking of a new plan to handle that trigger more usefully next time it occurs. Rehearse the plan vividly in your head a few times, like a mini-movie. Then next time the situation arises, put the new plan into action with as little self-questioning as possible, treating it as a decision that's already been made.

Best wishes!