Oh, I know how you are feeling. I've been there too, so many times (though with a slightly different soundtrack). I think you should forgive yourself for feeling down about it. You are so strong and independent and I'm guessing it is hard for you to feel this way.
But.
Maybe the permanent altering of your soul is a good thing. It was horrifically traumatic and nothing you'd wish upon anyone. But through the process you've become stronger, so much stronger. You're trusting yourself, you have confidence and strength for years, you are the best mom I've ever seen. I know you aren't an Esther Perel fan and the commentary on my thread about affairs making a relationship stronger is all laughable. But what she says could be applicable to you if you substitute yourself for the relationship... she says she would no sooner recommend someone have an affair than she would recommend they get cancer.
But over and over, people emerge from trauma stronger than before, and in the end while they never would have chosen it, the growth and learning it engendered is a tremendous gift. Think of all you've learned about yourself and about human nature. The next relationship you choose to participate in will be healthy and the next partner you choose to spend time and energy on will be worthy. I know it, you know it. You'll never allow yourself to be gaslit again. Meanwhile, your X will keep toodling away at his sad and unfulfilling life, and my guess is over time you'll have many, many more times when you're thanking your stars to be Ded from him than times spent wondering what happened and why.
The scar will always be there. But you're stronger than you were before and so much better off without him dragging you down.
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing