The truth OP is, brutal as it sounds, if he doesn't get his shit together and leave his children alone, they sure as hell will NOT grieve him, and most certainly won't be devastated.
Young children accept a bit of giving out to from parents, but your child is telling you she hates her father.
You are entering permanent damage area in your children's life.
If you feel unable to fully tackle this, him leaving the home would be a good interim solution.
The children are being relentlessly bullied by him.
I promise you that you could be dealing with depression, anxiety, self harming, acting in a few years and it will be traced back to this.
Secondary school pastoral care staff come across this all the time.
You can only do so much.
Suggest it when they are out of the house.
You cannot continue to walk on eggshells around his grief as he emotionally abuses your children and they then tell you they hate him.
The price is too high protecting him, rather than them.