My daughter in-law is going through divorce and has agreed

My daughter in-law is going through divorce and has agreed to joint custody of the children aged 5 & 9, although he keeps stalling the procedure by asking to gain more custody ie; half of all half terms and half of all holiday time whilst having them every other week.
Her husband has started a new relationship during the past six months & has taken the children to meet his new partner. He works full time, so how would he be able to get all these days from work? My daughter in-law works part-time around the children's schooling.
This situation has now gone on for 18 months plus with her having to sleep downstairs on the sofa and having to stay away from the house every other week (his weeks) until the children have gone to bed. Having found a new home to move too after the divorce and paying for a search, and other costs, her ex is still not agreeing to paying the final divorce settlement until she agrees to his terms (these keep changing)
Can you help and let me know how to get this finalised. The children are not coping well in this environment and it has spread to school as well
Thank you