As someone else said, Google limerence and see if that helps you understand that what you're experiencing is extremely common.
I struggled with it for a few years, the repeated intrusive thoughts could sometimes send me crazy with frustration. It was a miserable time and I very nearly made some stupid, terrible decisions. To the outside world you seem fine, but inside you're a mess of emotion and thoughts.
I tried most things the limerence websites recommend you try in order to snap the feelings off, but the only peace I ever obtained was by going no contact.
You say you would find that too sad and extreme. That's actually the limerence talking. You probably don't believe me, but if this was a friend who was causing you this mental trauma in any other way, you would cut them off. He did this to you. He started it and he had no right to. It's warped your view of reality. I gave it a name. I called my limerence the Limberbeast. I came to know how it worked and how it played with my mind. I even knew what times of day it would torment me the most.
You could spend years and years with these thoughts and feelings, or you could spend a few months feeling sad because you've gone NC. But then, get this, you'd have your mind back again.
What I actually found was that after a few months NC, the feelings had left, I had my mind back, and was eventually able to reconnect but in a normal friendly way. The intrusive thoughts are gone and I'm happy again.
I also decided to plough the effort and emotion I had spent dealing with limerence into the relationship with my DW. Every time I thought about the object of my limerence, I would instead think about some way to do something nice for my DW. The result is we have never been happier together.
Limerence nearly destroyed my life, actually, but if you take some difficult steps you can come out the other side and use the experience to be wiser and happier.