Useless father, hate his fiancé, big fall out rant

Hi all just really needed a rant as I’m fed up of constant arguing with my dad and my partner is sick to death of hearing about it and I’m even sick of moaning to my counsellor about it all.... I’ve got a really messed up relationship with my dad and it’s gotten so much worse since he got with his new girlfriend (now fiancé)

Fell out with my dad big time over a year ago as all he cares about is his new money grabbing fiancé and her daughters. They’ve been together a couple of years and getting married this year and ever since she came along he’s just shoved my sister and me to one side and has been all about those girls, like he doesn’t even have daughters. I can’t afford to move out, I live with my mum and my dad knows I’m saving for a house with my partner but he went ahead and moved his girlfriends daughter and her partner in my nans house after she passed away and gave them free rent for 6 months to help them out in saving for a house yet he’s never ever offered anything like that to me or my sister who both struggling financially to save and get on the property ladder. He shows so much favouritism to her daughters over his own daughters it’s sickening

He’s getting married this summer and obviously we haven’t been invited as his gold digging fiancé hates us and just wants all of his attention and money to herself and her daughters and she encouraged him to fall out with us. Been told by his side of the family that he’s going around saying they’ve invited us and we’ve declined the invite and chucking our toys out the pram when he hasn’t even invited us at all!! We don’t know when or where this wedding is even taking place!! Called him out on this tonight as I’m sick of letting him get away with this behaviour and it’s just resulted in yet another argument where he’s just lying and saying that his fiancé ‘wants to make amends with us’ and ‘wants us to be bridesmaids at the wedding’ LMAO the bitch and her daughters have blocked me and my sister on Facebook after she rang me up last year telling me to back off of my own father and ‘leave him to be happy’ 😂😂

He doesn’t see that this woman is just after his houses and cars and shes manipulated the situation into making my sister and I into the bad guys, when really she’s revelling in the fact that all of his attention and money is going on her and her kids and has made it very clear that she doesn’t want us spoiling that. I’m so done with it now and exhausted arguing with my dad and now thinking I need to just disown him and let him learn for himself when she marries him and then divorces him and takes all of his houses and money for herself and her daughters.... then he’ll come crying back and we’ll have to pick up the pieces (this has happened before - we fell out over a very similar situation with his ex girlfriend when he ended up almost bankrupt and homeless because of her)

I just don’t know what to do anymore. I’ve only got 3 sessions left of my counselling and my counsellor believes i need to cut him off for my own well being but I just don’t have the balls to do it, instead we just go round in circles and are treated like pieces of shit on his shoe whenever he has a new girlfriend/fiancé on the scene