Step-dad forcing me to put step-sister in my wedding

Hi everyone,

I’m in need of some advice. My step-dad is telling me I need to put my step-sister in my wedding or else he’s not contributing and will not be coming. Some background:
I’m 25 and we’re planning our wedding for 2022. My step-dad has always been extremely manipulative, it’s always “my way or the highway” with him. He has two daughters, one who would probably go out of her way to do something on my big day to ruin it, and the other who is my age and is just as manipulative as he is, we’ll call her Stacey!! Stacey is the daughter he wants in the wedding.
A little story on Stacey: her freshman year at college, she told people she was me and literally gave MY phone number out to people. I received a text from a guy asking to “meet him at the quad.” I did not have a “quad” at my school and I was in my dorm unpacking at the time. He explained that he was literally just talking to me but that was impossible since I was in my dorm. Stacey was also rushing that day and introduced herself as me. One of my girlfriends sent me a picture of her asking why this random girl was introducing her self as me, turns out it was Stacey. I sent a picture to the guy that texted me earlier in the day, he confirmed it was also Stacey. I told my mom but nothing ever came of it. From that point on, I really just kept my distance from her. We’ve never been close!!
Fast forward to now. Still not close!! I have my bridal party picked out, I’ve been ordering all sorts of personalized stuff to put in their proposals. I told my mom from that start that I didn’t want either of my step-sisters in my bridal party - I’d be more than happy to find a role for them but they will not be bridesmaids. She was ok with it, as I’m not close with them. But not my are-dad is saying that he’s not going to contribute financially, and that none of his family will come if she is not a bridesmaid.
My thoughts: This day is about my fiancé and I. He’s making it about his daughter by threatening that he won’t be involved if she isn’t. It’s only been a few months and he’s already “strong-arming” me on this. If he’s serious, I think it’s so messed up and he will completely sever whatever relationship we have with him. I obviously want him there, but I do not want my stepsister in my wedding.
Has anyone been through this?? Does anyone have any advice??