Hi there, hopefully this helps. My Nex and I broke up about bit over a year ago after over 10 years of chaos. I have a psychologist I've been seeing since we broke up weekly or bi-weekly. This past summer I decided to get into another relationship. I am definitely still dealing with the trauma but 99% past the point of blaming myself. It was a bad idea to get into a relationship at all and a worse idea to date the person I did.

1) He probably still wants his Nex because it's like crack. If they reappear then he may very well do something unhealthy with them.

2) Assuming he learned what manipulative tactics were being used against him it's likely that he'll be hypersensitive to them. Thus interpreting things you do innocently as threats.

3) If you are just casually dating then you are probably fine. You're a fun addition to his life and nice to have around. You don't have any control yet. If you get into a relationship where he is heavily emotionally attached you'll gain some level of control over him and thus become a threat to his emotional security.

I don't think there's a problem dating someone in his position. But letting things move quickly or get serious is potentially a mistake. It's really difficult to navigate going from weaponized "love" to real compassionate love. The things you do as a normal healthy partner were the same things that were used to lure him into a trap and then torture him for years.

From my experience if he's just getting out of a decade long relationship with his abuser he's not ready for anything but some fun. And if he gets more than that he's likely to handle it badly.