Father/Stepmother Divorce - Advice Needed Please!

Hello,

My father (66) has got himself into quite a situation with his wife and step-daugher. He doesn't know where to begin with sorting it out and so I have offered to try and help.

I have summarised his position below and have tried to be objective and unbiased otherwise the advice received won't be of use i.e. there is no benefit to me in twisting the story.

Situation:
My mother and father divorced many years ago
In 2011 he stared a new relationship
New partner had a teenage daughter. My dad agreed to take them both in and support then which he has. Her former partner was abusive (hence breakdown of their marriage) and paid no child support for the daughter and was of little help.
They were married in 2014. I didn't want him to as I thought both mother and daugher were troubled and the marriage would not be happy but he didn't want to be alone and perhaps thought he could make their lives happy - making up for the miserable years with her previous partner. They came into the relationship with no money whilst my dad had some but certainly not wealthy.
My father is self employed (always has been) and his new wife has always had some involvement in the business though this is minimal as she has no skills or experience and so he has largely been running the business on his own. It is also quite a physical job.
The relationship was OK (both were very antisocial from the beginning but i put this down to shyness and a lack of confidence) but things are awful now to the point where my dad can't have visitors. The mother's behaviour became clearly more erratic and unfriendly once they were married as though as they were now married she no longer needed to engage with any of my dad's family or me.
The daughter's behaviour was OK at first but got worse after she finished here GCSEs and has got much worse since she finished her A levels at 18.
For the past four years she has done nothing other than a few part time menial jobs for which she keeps the money.
Effectively the mother and daughter just loiter around the house 24/7 watching TV or on the internet whilst my dad works 60 hours a week to support them.
Both have refused to get any professional help for their mental health issues or even admit there is a problem.
My dad wants to retire next year and is already eligible for a state pension.
They are tenants in the house they live in (its linked to the business) and it will go back to the council when he retires leaving them nowhere to live.
There is no way that he can support all three of them on his state pension and no way they will be able to afford a 2/3 bedroom property to rent. Hopefully the council will house him but it will be a small property at best and he says the idea of being stuck with them 24/7 without the time spent out working scares him greatly.
He could live another 20 years and sees his retirement as a good time for them to go their seperate ways. I've told him he has done all he can for them and should think for himself.
He's worried how they will end up without him to help them. There is little he could do financially once they separate but on a day-to-day basis they might struggle.The daughter can be quite aggressive towards her mother and my dad is also worried what happens when hes not their to intervene.

My dad has very little savings but does have asset of around £50k and a private pension of £70k that he has been paying into for 50 years. Its doubtful that his wife has anything as she has never worked apart from the few years that she helped my dad out without the business.

Questions
I think my dad has good grounds for a divorce in that its a miserable relationship and she has done nothing to help. How would this process proceed? I have just touched on her erratic behaviour and my dad can provide so many more examples. I would assume that he can get an automatic divorce and that she couldn't realistically contest this?

Financially what would she be entitled given that the majority of what money he has was accrued was accumulated before they got together. When he and my mum divorced he was left with c£100k and now has less than this s the business has not well and he has essentially been keeping her daughter (she has rarely worked and when she has has contributed nothing). Surely she can't expect to have half his assets given the short miserable marriage and that all of the wealth was accumulated before they got together.

If she does have ground for a substantial claim how would this work? How could she get his private pension unless he cashes it in?

I would assume that the mother and daughter would need to be housed by the council (as they were before they moved in with my dad) but they would be less of a priority for the council as she is now an adult rather than a child as when they were last housed by the council. They are both fit and able to work but are unwilling to do so. I'm not sure what their options should be. She has another older daughter who lives nearby but she's happily married, does very little to help and certainly wouldn't have them living with her. She is actually more of a problem than anything as she seems to encourage them to get what they can out of him. She only turns up at the house when she wants something.

I'm hopeful that my dad can minimise the amount that he pays to her but I've said its a small price to pay to have some sort of a life away from them. Another concern is that they'll waste whatever he gives them and come back to him but as above thats better than continuing as they are.

I've recently discovered that my dad never got around fro changing his will over and so any monies would go to my mum (he is very disorganised and never got around to changing it). They get on well and this would certainly be passed to my siblings, myself and his grandchildren. My mum wouldn't attempt to keep it. To be clear I'm fortunate to be comfortable financially and so am not concerned about the divorce due to how it might affect me - my only concern is my father getting away from his marriage and having some funds to support him in his old age. I have said not to change it for now and certainly not to change it to his current wife.

Any thoughts/suggestions would be much appreciated? How best to progress quickly and keep the legal costs down?

I've never been divorced but my parents had a messy divorce and hopefully this can be avoided here and the stress and pain minimised for everyone involved.

I hope this doesn't sound cold - I do hope that my step mum can resolve her problems but each year things get worse and my priority is my father.

Thanks in advance