Is it inappropriate to respond to my ex's complaints about her new boyfriend keeping her awake by going over there to yell at him?
Why do you want to respond your ex?
I don't want to discuss it, I just need permission to leave
I understand you still care for your ex. Still, it's inappropriate for you to insert yourself in her life.
Fuck you.
There's really no reason for you to continue worrying about her in these simple situations with her new partner. It's time for you to focus on moving on, and finding happiness for yourself.