Well you must understand that your experience is not the same for everyone?
I'm a step child, I have a step father and I just can't relate to what you say, sorry.
I love my step dad 🤷 I'm glad he's in my life. My parents were shit together, I remember the arguments and the negative feelings in the home before they divorced and I was glad to be out of it. They were calmer, more engaged, better parents when they weren't together. They spent more time with me than they ever had before. I've never even thought of the fact I was unable to say 'mum and dad' tbh.
I also never really cared about going between two 'homes' but then I never really felt like I had two. I had my home, and then my mum's house and it never emotionally scarred me. I didn't think of my mum's house as my home, my dad's was my home. That was fine to me. I know some people think the idea of not feeling at home in one of the houses is absolutely awful but that was the way I felt and I don't even think it was a bad thing.
Having step and half siblings
And I don't really like that this is on your automatic negative list of things being wrong with being a step child. I love my 'half' sibling thank you very much! She is not a negative thing to me. She is not a 'bad deal'. She's my sister.
I'm sorry if some of your parents got it so wrong. But it isn't the same for everyone.