soooo tired, I understand the very human feelings you are having about this. I had some of the same issues when my ex-husband and I first separated.
Over time, those feelings changed as I built my own life.
I can't imagine, though, how betrayed you must feel---by a husband and a so-called friend---at the SAME TIME!
Your only course of action is to change yourself. Your feelings may not change at first---just like our feelings about our DCs---but your thinking and your behavior---now those you CAN change.
It takes work, and it takes focusing on other, healthy things and new ways of thinking and behaving in order to build a new, better life.
In addition to those already recommended, like Frankl, I recommend you read Boundaries by Cloud and Townsend. Also Brene Brown's work----all of it----is amazing. There are YouTube videos of her plus books plus even online classes you can take. Pema Chodron's work is another. All of these people focus on changing our own thinking...which leads to changed behavior...which in time leads to changed feelings.
Most of us get stuck in our feelings, and we believe those are the TRUTH, and we can't get unstuck. Feelings aren't facts. They are real and true but in many cases, I have so learned the hard way, we should not act on our feelings. We should make time to feel them and feel them honestly...and then wait a few days until we are stronger...and then take other, more appropriate action in most cases.
Hang in there. You've been done wrong. That is true. But now, how can you make your life right? That is the question.
We're here for you.