I am not sure 'forgiving yourself' is the right thing here.
Yes what you did was awful. What you did to that women was awful. You met her, chatted to her all while having slept with her husband. You carried on taking his time up, because YOU needed him. Then you told her, not what she wanted to know, just enough to hurt her. And not because she should know, but to hurt him. You refused to give anymore detail, though she wanted it. And you wouldn't. Then you gave her everything, to get at him again.
Any hurt you caused him, imo, isn't a big deal. He caused this. But you repeatedly hurt this woman again and again, as a game. Like she isn't an actual person just an extension of him and a tool for you to hurt him with.
I am not sure you can ever fully forgive yourself. And that's not to be awful to you.
Instead of forgiving yourself, I think you need to learn to accept what you did. Look into the reasons why. Look at wether your marriage (in name only) is really the right option. Did that contribute to this? Is tbe finances really worth it, when you are acting in ways you don't like.
What's causing you to act like this towards people like his wife?
I am sure you are nor an entirely awful person, just because you have done awful stuff. But I am sure this isn't who you want to be. Accept what you did. Accept it was awful. Accept that you need to do alot of work on yourself, so you don't act like this again.