I'm not really sure what to tell you to do except that maybe to try to put something near the doors to help block them so he won't dart out. I've only had one door dasher and that was Sky. He was found as a stray so he was used to being outside. Luckily he couldn't get very far because my front door leads into a hallway. I put up a baby gate for a while so that if I was carrying something he wouldn't be able to door dash. It worked a little bit. Luckily over time he became used to being an indoor cat so now everything is fine. Good luck.