Sorry that happened to you and your children. How awful.

I can only offer my own very fallible opinion.

My training is in ethics and so I have been taught that voluntariness is something that isn't always all or nothing. There are degrees of voluntariness.

However, I believe [and could be wrong] that unless a person has a complete break with reality as in a psychotic breakdown, there is always some voluntariness in human actions and therefore some amount of human responsibility.

Given that ethical idea, I think it is not reasonable for a person to claim to be totally not responsible for their actions. Mental illness can be profound and perhaps can reduce voluntariness and therefore responsibility down to 1% but 1% us still something voluntary and therefore something either praiseworthy or unpraiseworthy.

I can't claim to know your ex-husband's frame of mind moment to moment over the time period you were with him, but I believe that unless he was in a total and profound psychosis there must have been some elements of voluntariness in at least some of his actions, and therefore some responsibility.
Mental illness, diagnosed or undiagnosed, in my opinion, is not something that destroys human freedom completely except in exceptional cases.

One of the hardest things a human being can do is admit to blameworthy behavior. It is much easier to use the various determinisms of genetics, upbringing, social conditioning and other impediments to shift responsibility totally away from ourselves.

Sometimes a person with a fragile sense of self-esteem cannot bear to accept responsibility for actions but unless they are completely without conscience, I suspect they do experience things like guilt and shame.

I know from personal experience that sometimes guilt moves me to try hard to shift blame away from myself. Perhaps that is what your ex-husband is doing. It might be that his seeming lack of any remorse for what he did to you and your children springs from profound guilt.
In other words, he only denies all responsibility because deep down he feels profoundly responsible. People sometimes try to project the very opposite of what they feel. A person who feels cowardly may go to great lengths to project a macho image. A person who feels inferior may go out of their way to project an image of superiority.
Maybe that is what is happening here. Maybe your husband is trying to project an image of total innocence because he feels profoundly guilty. What do you think?

Perhaps there will come a time when your husband will be able to take at least some responsibility for his actions.

An insightful, mature and thoughtful person would be able to look at himself or herself with some objectivity and see that they are not just a machine and that while there may be extenuating circumstances for their behavior, they still have some responsibility even if minimal.

In the meantime, to have some peace of mind, you might want to consider seeing your ex-husbands attempts to shift all blame away from himself as a sign that perhaps he feels great guilt and shame that he cannot bring himself to admit.

Psychologists say that there are true sociopaths, individuals without empathy and conscience. Sometimes such individuals end up in the criminal justice system at some point. I am not a psychologist so I don't know too much about that.

It would be nice if your ex-husband apologized to you and your children for the abuse he inflicted upon you, but I don't know if such a thing will happen.

So sorry that I do not know how to be helpful to you in this matter. If I was in your shoes I think I would think and feel exactly as you do!