Violence
I am no expert, so please take this as mere observation / opinion.
Violence is the basest form of human nature. We all experience violent, narcisistic and abusive thoughts but our intellect and social conditioning usually place boundaries on how we act these out.
Dementia erodes those boundaries as our intellect and social conditioning are located much higher brain functions than the emotional centres which govern our basic instincts. Brain damage, (there is no other word for it), may be due to a single trauma (like a stroke) in which case the condition may stablise or even improve as the brain re-wires itself and adapts. People who have suffered severe head wounds can exhibit similar behaviour. In such circumstances, time is often a great healer and it is perhaps worth exploring the prospect of a long-term positive outcome as a family for them and for you and your children. You will need to adapt as much as your partner, but that's the same for everyone, (dementia or not), and families are stronger like that.
Sadly, other forms of dementia are progressive and in these cases the degeneration in a person's behaviour is likely to be progressive too. In cases of aggression, it might be expected, (especially in early onset cases for subjects who are otherwise physically fit), for such dementia to start expressing itself through sexually inappropriate behaviour also.
If alcohol is a factor in your husband's lifestyle (and abusive tendancies) then you need to be doubly cautious. Alcohol dependancy starves the brain of oxygen. When drunk, in most cases we typically exhibit (temporary) signs of a stroke. Aphasia / disphasia, vertigo and short term memory loss being amongst the most common. With alcohol this is quite often compounded by the narcisistic feelings of strength, happiness and invulnerability, leading to exhibitionism, violent and/or vulgar behaviour. Sound familliar? In some cases alcohol simply puts them to sleep. In others it removes all inhibitions, including their personal safeguards.
For someone already suffering from dementia, this is a poor combination. In all cases, you need to realistically assess your own thresholds of patience, tolerance and safety for your own sake and for your children too. But the likely outcome is also a factor for which you need specific advice in your own particular case. i.e. Is this likely to get worse, better or stay the same? If your partner is unaware of their behaviour and generally uncooperative then your options are significantly more limited than if they were trying to "work with you". The severity of some conditions quite simply make the patient incapable of helping you to help them, and certainly in the case of any violent / sexual abuse I would recommend early intervention by the Social services. If at any time you are in fear of your or your children's safety then most certainly you should call the police without hesitation. If the abuse is merely verbal, then how long can you and your children endure the psychological battering? It is a judgement call which only you can make, but my advice to you is DO NOT refrain from taking appropriate action in your own best interests, simply out of your understandable sense of duty.
Would the children prefer an absent father whose memory in their formative parts of their lives would be treasured for ever, or to live with an abusive man they never could respect and perhaps grow up to fear and to hate?
There is a very good series of adverts on telly at the moment dealing with violent abuse called "if you could see yourself...". This, of course, is a general message to all of us, asking our cerebral cortex to communicate with our lower brain stem before acting on impulse. But the same principle applies, I think, to patients with dementia - except they can't do anything about it themselves. I prefer to think of the person with dementia as existing within a bubble where they are the most important person in the world. But if the person they used to be "could see themselves", they would be saying to you, "help me to stop behaving like this". When you get to the end of your tether, the best help you can give them is professional help, so please don't feel guilty about taking the steps you need to take before it's too late.
Best wishes,
LDMax