I read the other thread and I'm really sorry your family has put you in such a crappy situation. I can't say I have any experience of what your going through BUT I do know what it's like to wash your hands of a parent!
Without getting into too many details, my parents split up just before my 17th birthday. Prior to this I was a real daddy's girl, but after I started to see my dad in a different light. He made out he was the victim, but 1 day after he 'persuaded' my mum to move into a friends house (with my sister age 12 and brother aged 8) he had a chat with me and told me he was a man with a mans needs and couldn't go long without a girlfriend. One week later I bumped into his 'new' girlfriend coming out of the bathroom at 7am.... Mum was staying about 45 miles away so I had to stay with him in the family home in order to go to college.
Over the next year he basically lived with his 'new' girlfriend at her house, but told everyone else that he was living at home with me and that I couldn't be believed about anything as the split had affected me mentally! He was so persuasive that even my mum questioned how much I told him about his behaviour was real. My family still skirt round the issue, but they weren't there! He banned my BF and my boyfriend (now DH) from the house for made up reasons which would have left me completely isolated. I bought my own food etc from a weekend job, he didn't pay any bills and he expected me to fend for myself as an adult but still act like his little girl.
The final straw was when he was violent towards me, he only did it once but that was it. We changed the locks and mum reclaimed the house.
Since then I Can count on one hand the amount of conversations I've had with him, all forced by circumstance. I havent seen or spoken to him in 7 years (which was when my brother was in intensive care after an accident).
I have no regrets about cutting him out of my life, except that I've also lost all my relatives on that side too, I tried seeing them but they just kept going on about how hard it all was for him!!
You don't need family like that.
Sorry this has gone on so long, I hope you manage to sort things out OK.