If he is violent, then you need to be careful. Consult a lawyer. A lawyer will tell you what needs to be done and if it is possible to file a restraining order if they are available in your area. Before any of this start your own bank account and store some money in there. If you are not working or only part time there may be state benefits you can use to transition to your new life (Food, Medical, Cash, Section 8, TANF, ect.) If you fear for your life and the safety of your children they may at the very least offer a temporary one. If they issue a temporary one, you will need to change the locks in the house and get an alarm system if you don't have one. File all the necessary paper work and include a temporary custody arrangement. Once a again, a lawyer will be able to give you all of your options available to you under the law, because even if he is unstable he is still their father. You can push or ask for supervised visitation until he can be evaluated by the court. Just remember what is good for the goose is good for the gander. Depending on how young your children are they may make you the default custodian parent. Most courts try to maintain the children in the live style they are accustom to, Meaning they want to keep them in the family home, involved in their community activities, and place them with the primary care giver. UNLESS YOU HAVE TO FOR REASONS OF SAFETY DO NOT LEAVE THE MARITAL HOME. Take an inventory of all property: Cars, collections, art work, electronics, debt, jewelry, kitchen appliances, ect and get them appraised if possible. When you file the divorce paper work you will need to list all of this and you can submit how you think the items should be divided. When he responds to your paperwork he will be allowed to make his suggestion for division as well. The division of property, debt, and real estate may be settle in mediation or decided on a by a judge. Remember that the judge will usually try to spilt things 50/50 but he will also look at who has the financial ability to be responsible for the items. Example being if he makes more money then you and the judge awards you the family home, the judge may order him to continue to pay on a portion of the mortgage or pay you alimony to cover life expenses not covered by child support. He may order that all common property must be liquidated and divided after sale. In a divorce you really have to be prepared for anything.
Have there been any Domestic Violence charges on him or noise complaints from the neighbors? If no one has reported his behavior it may be harder to prove. Get notarized statements from family, friends, and neighbors that have as much detail about his temperament as possible. Collect copies of all bank accounts (all joint and private accounts), pay stubs (His too), tax returns, birth certificates, social security cards, and keep them in a safe place-With a family or a friend would be ideal.
Start a buddy system with family and friends. Some one who can check on you and your children regularly. I am so sorry that you are going through this. No body deserves to be afraid of their significant other. I got out of an abusive marriage and I was lucky to leave alive.