If mum dies of cancer, how can i live with dad again?

Mum has been diagnosed with a second cancer. I am worried for her, worried for Dad and worried for myself.

I would not want to move in with Dad if Mum died but I can see no other option that wouldn't amount to abandoning my father in his infirmity, and that would be despicable.

Dad does nothing in the house -and he does this, not because he is incapable of doing anything, but because he can get away with it. He had a stroke 10 years ago that reduced his balance and dexterity enough that he couldn't climb ladders any more and thus practice his trade, or walk for more than 5 minutes without needing to rest. He can however build and paint intricate models and design engineering hobby projects, and this is how he spends his days. Effectively, playing.

He does nothing in the house. He leaves his laundry on the floor next to the laundry basket for Mum to put in it. He dumps his dirty plates in the sink for Mum to wash. He never seems to cook. He never gardens. He never mops the floor, cleans the toilet, dusts, vacuums or shops. He takes things out and leaves rooms a mess and Mum picks up after er him like a servant. Mum says she doesn't mind - she enjoys housework. I can't imagine this being true. It has been this way for decades - his excuse before was that he had a strenuous job. Now he doesn't have one. But he still has Mum run around after his every whim and pick up after him like a toddler. She has considered applying for carers' allowance because short of washing and dressing him, she lets him do virtually nothing for himself.

There has been an assumption on the part of my dad and my brother that I should do as Mum does, as housework is'women's work', even though Dad has not had gainful employment for 10 years, and Mum had to stop her employment 3 years ago due to stress related cancer.

But if Mum dies of cancer and I have to look after Dad, he will expect me to run around after him like a servant. My relationship with Dad is already stormy. I have seen how selfish he can be - how everything he does do around the house, if he does anything, is because if he doesn't, 'Mum'll go ape'. Not out of concern for the house, or for the wellbeing of the people in it - just because he knows that Mum's anger awaits him if he doesn't do it. It is like he doesn't care how Mum experiences her home life at all - he just doesn't want to be shouted at. He reacts to emotions with things like 'Oh, don't look at me like that' or 'Don't do that' - as if all that matters is his displeasure at not having a smiling happy person front of him.
He has also used the threat of Mum's anger/upset to threaten me into doing things. He uses guilt trips to coerce but does not seem to feel guilt himself - all he feels is shame (feeling bad because other people see and disapprove of your actions). 'Sin' to him is just whatever brings shame on him in the eyes of others. Even buying birthday presents is a matter of meeting expectations and winning 'brownie points' with Mum. It all just looks calculated - about getting his wants and needs met and saving face. I could not bear to be his slave.

And yet if Mum dies and I don't look after him, he will be helpless to look after himself. I cannot just let my father rot away in that old workshop where he sits tinkering. That is what he would do if she wasn't there, doing everything for him. She says she does everything because she cares. But she has not only increased his sense of entitlement; she has debilitated him.

How could I care for my dad without becoming his slave? He is emotionally manipulative and has become more aggressive since his stroke. He does not seem to have concern for anyone else's feelings, except if them expressing their feelings could result in trouble for him or make him look bad in front of people.