I grew up with an incredibly jealous step mum, she never wanted me in their lives and always treated me like a second class citizen, I was never allowed to be alone with my dad and I lost count of the amount of hurtful things she'd say or do over the years to purposely exclude me. I never felt comfortable at their house, I never felt like I fitted in, but I persevered because that's what you do when you've been exposed to it from a young age, you imagine it's your fault and that she'd like you better if you were more like she wanted you to be.. looking back on it from an adults perspective, it's horrible.
I think you'll find it hard being in contact with your dad and not her, I had to NC that whole side on my family in the end after the last straw, everyone was in on a big secret about her health and I wasn't told 'because she didn't want me to know' I couldn't take any more after that, it was the final fucking insult and I'd finally had enough.
If you want a relationship with your dad then I'd let him come to you or meet up on neutral territory, but don't be surprised if he pulls away from you, as from the sounds of her she won't be happy with that. Don't take it personally though, a lot of people choose the path of least resistance.
I'd still engage with your siblings, but lay it out to them what has happened to make you come to this decision, but stick to the facts and try and keep emotions out of it, hopefully you can still maintain a relationship with them, but they deserve to know the truth.
Good luck OP, the scars from childhood sometimes last a lifetime, but you've got your own family now, so don't waste another second on her bullshit, yanbu to cut her out your life for good.