I actually feel lighter.
I did this with a therapist's help. I think there's a method called confrontational writing that can be therapeutic. Pretty sure I wrote over two dozen drafts and each one helped me get closer to putting down on paper what happened in the marriage to lead to this point. It clocked in at 10 pages.
I remember writing it and the catharsis of sending it. Can't remember the response other than it was classic.
Someone once wrote it takes one month for each year of marriage to heal. That's for a "normal" relationship. For a high-conflict marriage it's more like 2 months for each year.
Obviously that's a rough estimate and everyone is different but the month I felt great for the first time in forever was exactly 2 months for each year of marriage. So 11 years of marriage = 22 months before I felt great about where I was at.
You're in the roughest patch now and things like sending the letter are important because it's for you.
Also, this is probably a bit too candid but you're in no shape to help her given what's happened.
For many people with codependent traits there's this almost grandiose and even delusional belief in our abilities to rescue others. I look back at my codependent delusions and it is almost comical how deluded I was.
I'm reluctant to compare people to dogs, although I love dogs so hopefully this isn't offensive. Codependence is almost like trying to retrain a dangerous dog by letting them bite you more. What is often more effective is to have a skilled trainer with good boundaries and a deep understanding of what a reactive dog needs and why, then working almost dispassionately and patiently to achieve progress. Even when a dog is rehabilitated, you have to keep those boundaries in mind at all times so a bad event doesn't happen.
You can't be rescuing others when you're still trying to figure out your own wounds much less how to care for them so you can heal. Maybe for some people the stars align and they can do that but most of us have category 5 damage and the rebuilding requires total focus on our needs.