His parenting style is so contradicting!

Okay, so I don’t typically post on here but just a small back story. I have been dating this guy and we’ve gotten close very fast. He has a 6 year old daughter whom I adore and we both want to try to have kids in the future and his daughter even wants a brother or sister. Although there are times when he gets so stuck on being upset about something little and his daughter gets attitude and his reactions are that she should have done better or he is really mad. She is always afraid to make him mad but they both get stuck in being sad and mad and this can last hours and it’s practically a daily thing when she is with him and not at her moms.

Now, before I continue let me just say he is a great dad and we do fun stuff and he does great in my opinion other wise. It I am afraid to over step. Because I’m not a parent nor am I her parent so here the line gets really confusing.

The other day he got upset that she left his water bottle for her at her moms when we picked her up from school. She responded with attitude saying kids forget things! And he got more upset and she started crying saying she always makes him mad... while we were in the car she was still sobbing in the back and I squeezed her leg and tickled her a bit without her dad knowing because I didn’t know if he would get mad.

Well I got a chance to talk with her as we went out to eat after school while he was over ordering we were sitting at the table and I asked her why she did not apologize for forgetting her water bottle? She said she didn’t want to she just wish she would remember. So I asked her why she didn’t tell her dad that and tell him she would try harder next time because she wanted that. And she was so nervous again.

She said what if he gets more mad, I assured her he wouldn’t. Then she wanted me to tell him, but I told her this was something she needed to do because she made the mistake.

She got the courage to say she was sorry and she would try harder next time not to forget next time and he was happy told her thank you and he loved her.

When he walked away she said I DID NOT EXPECT THAT!

well they were both happy and we moved on but stuff like this happens so often not only with his daughter but family and me. He gets so stuck on things needing to be the way he planned them to be and gets a bit petty when it isn’t.

ANY SUGGESTIONS?! I’m doing my best as a girlfriend and never been a parent and to find my place and help out.

Thank you for anything. Please no hateful comments, we are in this amazing relationship after being divorced and we both have our issues and I know I do too. This is just one thing that I am not sure how to react to all the time.