How about I ask my dad to break up and kick out his girlfriend?
Why do you think he should do that?
I want him as a single dad
I'm sorry that you're having issues with your dad's girlfriend.  It's totally normal to have some resentment towards a parent's new significant other.  Just give it some time!
You just don't understand! All he ever does is hang out with his new girlfriend and not me.
Have you tried talking through your issues with him to see if he'd be willing to spend more time with you? It's normal to not like the new relationship your parents enter because it can be hard to accept them, but a few well placed conversations with your father might make everything easier to handle.