What can you do if you are scared your ex-husband who is a father to your daughter is a sociopath?

There is nothing you can do about it being true if it is so. If an ex husband is truly a sociopath and relations are ongoing, it is imperative that one learn as much as possible about self protection and protection of children/teenagers. Sociopaths vary in their dangerousness to others but are by definition superior manipulators of even the most educated minds.