First off, big hugs to you! Breakups are so tough, and you deserve big hugs and all my best wishes and thoughts.

Second, I agree with the other posters so far. It is not your responsibility to "help" him by telling his father intimate details or anything else. Sure, talk to him if it will make YOU feel better, but be careful about those details. That's for your ex to figure out and work on (if he wants to/eventually), not for you to push.

Focus on you and your best interests. Particularly, focus on the financial, and don't lag about it. Get the house and mortgage in your name (and your name only) asap. Same for bank accounts and other accounts. Change the locks. When you can, I'd sell the house and move away from the family. Too close for you to move on from.

And remember, this is probably a good thing, that this is happening now, before the marriage, kids, other stuff. I know it sounds hollow now, but some of us have a bit of experience in these subjects. You say you are surprised, but perhaps, as you go through the process, you will find that it perhaps was not such a surprise. Already in your post you discuss issues that bother you deeply. Ignoring them rarely works.

And just be. Feel what you feel and let yourself cry, get mad, etc. And give yourself a big hug. And don't forget to watch out for yourself first and foremost.

((((assumed name)))))