If a spouse is insecure, then I would find ways to help bolster his (her?) sense of self-worth, by admiring and appreciating him early and often. Be sincere about it, but every time you find yourself thinking anything nice, give voice to it.
If the spouse is insecure but in denial about that, and trying to control the other spouse, it will be hard to break through to them. You have to understand their psychology if you are going to do anything useful. This means creating a safe environment for him to talk. It means listening and not defending yourself all the time. She has to listen, listen, listen and bite her tongue the whole time. Her goal is to understand him, not defend her individual actions. If she gets in defensive mode, forget about it.
The goal is to find out what worries the spouse. Why does he need to control? My guess is that it has to do with a fear about being lovable, and a worry that she will leave him once she figure out how no good he is. This is probably not a conscious fear, unless he is a pretty self-aware person.
The other thing that would help is if he does become aware of his behavior and what is behind it. This can come out in counseling, but it seems that is not an option. Perhaps the wife can serve as counselor, but that’s tough, too. Again, listening is probably the best that can be done here. Letting him talk until eventually he tells himself what he is feeling and why. Then maybe you can work on it in a more conscious way.
But it’s tough doing things without the awareness and help of the other person. It’s actually a form of manipulation and he’ll catch on. So it would be better to explain overtly that you want to try to listen better, and understand him better because you think this will help both of you. Who knows? Maybe he’ll want to join in.