My ex ia also like this. He can take a conversation that is meant to help our kids and twist it into something about himself or about "how evil I am". It is twisted.
It sounds like he is not listening to you at all as he is wallowing in whatever he feels he needs to wallow in.
You are so strong and what you are doing for your daughter given what you are going through shows what an incredible mom you are. She has fears and she can now share them with you. You are her rock. He is selfish. She needs you. Not too sure she needs him. My ex tries to negate the kids' feelings. Feelings are just that and as a child to be told they are wrong-well, it might be good to stay away from that for her benefit.
Do you have others who you can talk to about your daughter's worry box because they are real to her and you too. It sounds like you reached out to your ex expecting something he sounds incapable of giving. This has to be a hard time for you--do you have someone you can reach out to for you? Your little girl has a phenomenal mom.