I think Trippin hit the nail on the head.

Your wife seems to have quite a cruel streak. She seems out to punish you. No one turns into this kind of person overnight. It seems like you've been kind of innocent and naive to your wife having the potential for this level of nastiness. It's like you never saw it coming and still don't think of her as a basically mean, self-centered person. You might want to discuss with your therapist what seems to me like a tendency you may have to idealize a person you feel loyalty toward.

As heartbroken as I believe you are, I can't help but think you may have a better future ahead of you with this woman out of it. Just don't get stuck with the same type of woman again.

You speak about having a therapy goal of making yourself "a better man" than you are for the next relationship you get into. IDK, but it may possibly not be you who needs the makeover. Instead of thinking that you need to become a better guy, maybe you should be thinking about seeking out a better type of woman. I suspect you may have been selling yourself short and blaming yourself too much. (And I don't often say that to posters of threads.)