Nolife
First off, I'm so sorry you have a reason to be here. But you've come to a good place.
You are understandably incredibly emotional, so try to take some deep breaths. Stress is really hard on your mind, body and soul.
I remember reading your story when you first posted, and my bullshit meter went WAY up when you talked about the under-the-covers incident with your SIL. I'm glad you were able to get at least a little clarity on that situation by talking to the SIL, as much as it is painful to hear. I'm sure it was made all the more painful by the fact that your husband would not come clean about it in the first place.
I totally get the impulse to try to understand your husband's way of thinking. We as humans tend to project our own thoughts/feelings onto others. Which is why I also completely understand why you think that he just must not have thought these things were wrong (like the being under the covers with your SIL incident). You yourself know that to be wrong, so you can't possibly understand why anyone would do that thing, unless for some reason, they just did not know it was wrong.
However, I will tell you something my therapist told me when I was going down a similar line of questioning. I was concerned about similar things - how could someone do something which is so obviously wrong? He must have some kind of disorder that prevents him from knowing right vs. wrong, I thought to myself. That must be the reason why the loving person I thought I knew was able to turn into such a monster.
My therapist said: Look, if he didn't know it was wrong, he would not have had to lie about it. The good news is, that means you didn't marry a psychopath. The bad news is, you married a huge asshole.
Now that's overly simplified, as psychopaths and sociopaths have no or very little sense of right v. wrong, and yet they still lie all the time, put simply, to avoid negative consequences.
But the point is, those who have nothing to hide, hide nothing. You've known all along that his stories were bullshit. He even knows they are bullshit. He lies about it to protect himself from the very real consequences he might face if you were to know the full truth.
He then tries to use your separation as a reason he felt unloved, and therefore deserved to sleep with someone else? Fuck that noise. To paraphrase another poster here, there has to be something profoundly fucked up in a person's brain for them to think that someone else's genitals is going to fix their own emotional problem.
Therapist said he has brought all this on us with life long lies. His thoughts and assumptions and his senerios creativity in his mind of what I was doing and who I might be doing it with while we were separated and his choices brought this on himself and us with his lies and taking my life, my choices and trying to punish me with his thoughts going through his his head during our separation and continuing my entire life 38 years every argument.
Your therapist is spot on. Many call this "stinking thinking." You could also call it "catastrophizing," or "disordered thinking" or any number of things. I like to call it what it is - the bullshit excuses he told himself to justify the choices he made to do what he wanted to do. Because unless there was a gun to his head, it was a choice. Full stop.
it hurts that he thinks that the senerios in his head were real and I set out to hurt him. I feel he did this us with his jeliousy and creativity in his mind.
Many of us betrayed spouses have heard similar sentiments. That they thought we didn't love them, and that's why they did what they did. But again, it is very easy to poke holes in that argument, because of course, if you thought I didn't love you, why wouldn't you just divorce me? Why wouldn't you talk to me about it? Why would you instead choose to go behind my back and lie about it? If what you really wanted was for me to love you, did you seriously think that sticking your penis where it doesn't belong was going to make that happen? Any person capable of rational thought knows that this isn't the answer.
He has lied to you for 38 years. Not just to you, but to himself too. Because that's what justifications are really, they are the lies you tell yourself to make the very wrong thing you did feel acceptable. They begin to believe their own lies, because it's the only thing that takes away the pain of that shame. 38 years. That is not just a habit, it is a way of life. I agree with annb, he has shown you who he is, are you ready to believe him?