Contested divorce and kids custody

Dear Sir, My marriage of 12 Years has been a torture and now kids are getting effected by this. Last 5 years were are living in Muscat, Oman where I am working in private company. Every day there is fighting at home, My wife is Sadist she blames, me, my friends and family for a bad marriage and constantly doubts that I am having an affair with somebody and constantly making video whatsApp calls me when I am in office and calls my land line in office - If i do not answer in 2-3 rings or while I am driving to and fro to office (I have no one in my life or I have ever had) She refuses to talk to parents and wants no body to involve and solve issues ourselves or go to police station here in Muscat, Oman. FYI - I have not take any dowry, Ulta I have paid back the marriage expenses my in-laws spent as they are good and financial in bad shape. My life is open: Early morning I go to Office > for Lunch I go back to home at 1pm > 2pm then go back to office till 5pm - 5.30 pm I am back to home > 5.30 pm to 12 at night I am playing with kids or watching sports/TV. She still doubts me constantly checks my home / my car / keeps calling abuses me of imaginal girl...... its mental torture. My son is 6 yrs old and Daugther is 18 Months - I kept quite till now thinking she will be ok and I cannot allow children ( I love with my life) to suffer. BUT NOW IT IS TOO MUCH. I have so much stress and health issues also are coming up. My Question is : 1) Mutual Divorce is less likely as she is a sadist, so how should I handle contested Divorce. 2) Once I file for contested Divorce, What happens to Kids (son 6 yrs old & Daughter 18 Months)? 3) How can I take custody of kids ? 4) She keeps threatening me about false cases, causing damage to herself and kids and creating sceen and spoiling my family reputation, effecting my old age mother (my father passed my 3 years back) How do I save myself from such things ? Thanks a lot Raj Shekar