Yes I think that’s right BlueBelle, but not all fathers who are abusive are abusive to their children, but instead only abusive to their wives/ex wives. Unfortunately abuse to the ex wife does have an effect on the children, especially if they’re not babies.
I haven’t seen any suggestion from the OP that the father is abusive. It’s my opinion that he is intransigent and all parties are unwilling to compromise. This doesn’t bode well.
When we were in New Zealand visiting our daughter and grandchildren, when the children were with their father, my husband spent a lot of time decorating for my daughter, building a rabbit run for our grandchildren’s rabbits, doing her garden, building flat pack garden furniture, and other jobs to help her. I took the opportunity to spend some I-I time with my daughter and we went out for lunch a few times at the weekend when she wasn’t working. I also did absolute mountains of washing for her. Because of her ex’s very difficult behaviour and refusal to pay the child support the authorities have told him to do, we bought tanks full of petrol for her and groceries when she had no money left. He would see his children without food rather than do as ordered by the relevant authorities.
There isn’t a suggestion that this is the case here, but we have scant details. The four adults need to compromise, it’s that simple.