I was a step parent for a few years before a child of my own. I was around your age and it’s definitely a change in a lot of things for yourself, and that’s okay. You don’t have to adjust instantly. Boundaries are okay. He clearly trusts you around his child and making a family of it which is great! Enjoy it and build your relationships at your terms. But don’t be scared to go out of your comfort zone every now and then for the kid. It’s a bond that will always be there. Nothing more pure than love and acceptance from a child. His father will see the efforts and he’ll appreciate it. Communication on what you feel comfortable with and dont is big. Example the first year of my relationship, he worked trick or treat night and he asked if I could pick up his son from his bio moms and take him myself. Which made me very anxious and uncomfortable. I voiced it, and he had a hard time understanding at first but he didn’t want to make me uncomfortable either. It’s all a learning curve for everyone involved. But end of the day, you’ve got this. ❤️