I agree with one of the other people; make sure that you’re in a position where they have no ability to contact you, and you will never need to contact them, and then send it. That means things like a new address in a new city, making sure that they’re not on anything like student loans, etc. You may need to cut a lot of other ties as well; abusive families tend to use friends of their victim to keep tabs on them. Really severing ties in a way that is very, very hard for a determined abuser to track is hard, but i’d suggest taking as many of those steps as you can prior to throwing that particular bomb into a group chat.

PS - I think that you can go farther with you dad. There are a lot of great quote from Jesus–assuming that he’s Christian–that would be appropriate.