The more I look at your earlier post the more I'm actually a bit judgemental of how you've tried to spin this upfront when you later admitted that they are in a relationship.
You're doing mental gymnastics to present this as something different to the reality of the situation, which is that an arsehole with a girlfriend in love with him hasn't got the bollocks to break up with her and doesn't want to miss out on using her connections to access a lifestyle he enjoys, so has told you that you need to wait your turn to date him.
He’s sort of single, sort of not single.
False, he has in fact told you he is in a relationship with her.
He’s entangled with a woman who he has developed an emotional dependence on. She fancies him and he doesn’t fancy her.
But he's told you he's in a relationship with her, even if they don't kiss / shag.
They’re friends and she keeps breaking off the friendship because she wants more and he doesn’t.
They aren't friends. They're in a relationship. He has confirmed this.
They see each other once a week.
Because they're in a relationship. He has confirmed this.
So she is kind of like his girlfriend except he doesn’t fancy her and they don’t have sex.
She isn't 'kind of like his girlfriend'. She is his girlfriend. He has confirmed they are in a relationship.
How old are you all, out of interest? I haven't heard a 'we're seeing each other but she's not my girlfriend' since I was a teenager.