How can we get the divorce finalized sooner than have it drag a long for months and years and have the custody as well?

My sister is going through divorce. Her soon to be ex-husband is contesting the divorce and is fighting back. He threatens to drag the divorce with intention to deplete her resources, which is working since the attorney charges by the hour. He is also pushing for shared custody. This person is a radical Muslim who was trying to enforce Sharia law on my sister, which is a moral code and a religious law of Islam that deals with many topics addressed by secular law, including crime, politics, and economics, as well as personal matters such as sexual intercourse, hygiene, diet, prayer, and fasting. This is one of the reasons she wanted a divorce. He has sent a letter to family members saying that the son should be raised according to Sharia. He has ties in Kuwait, Iraq, Egypt, Qatar, and Jordan. His threats of taking the son away so the mother will not see him again were continuous since the day the child was born. He in fact has stated in emails that the son is his right according to Sharia and the connections with the mother should be severed since she is not abiding the Sharia law. This person has tried to commit suicide before and was committed to a mental hospital for four days. He has history of domestic violence in Texas and we found out that an ex got a restraining order against him in Illinois. Thank you.