For me, I found that part of my always having to know the truth was so that I felt justified in my feelings. It was my way of trying to protect myself from others thinking I was the "bad guy". I wanted others to see that I was justified in feeling the way that I did, reacting as I did, etc.
For me, I was the worst concerning AH's parents/family.
I have just recently realized that I know the truth. I do not need to justify my actions, thoughts, feelings etc anymore. Not to my in-laws and not to anyone else.
Inner peace - quite the concept, isn't it? LOL. But it took me a long time to stop trying to prove things about AH and gathering proof. You'll realize someday just how much time and energy you put into your A and you'll realize that you are obsessing over something/someone that is out of your control. Until then...I can only tell you that I feel for you as I recall what that is like.
Please start focusing on you!