Ok you want practical help. DC all teens so first thing is look for a full time job. DC taking themselves to and from school and letting themselves in of an evening because you're not home yet is fine. Set up a bank account in your name only, if all you have is joint ones. Start gathering up financial info, which will be needed to decide on split of assets in a divorce. Get legal advice regarding the divorce. All that is stuff you can do right now without telling DH.
If you need to extricate yourself slowly due to fear of violence contact Women's Aid for help making a plan of how to do it.
If you're after a quick getaway then look for somewhere to rent now. Try to make it somewhere safe and free from damp, don't worry about stuff like DC having to share a room or whether there's a garden. Gather a bag ready to go with all your important stuff like passports, phone and charger, your financial info, jewellery, anything else precious to you, hide it somewhere he won't find it. Have a clear out if you can, black sack all your favourite clothes for your best friends house the charity shop. Set up Universal Credit if applicable. When you get the keys to your new home, leave while he's out. You don't need to tell abusive people face to face that you're leaving, it's a good idea not to for safety sake. And you don't owe them any explanation of why, at all, ever. "The relationship doesn't work for me any more and I'm ending it" is all the info they need.
After you've left change address on everything, including for DC. Car log book and insurance, driving licence, GP, work, bank, pension, phone contract. Tell utilities at old address it's no longer anything to do with you so remove you from the bill, take meter readings if you can. If there's money in a joint account take out half, then tell the bank that you don't want joint account any more because you've split up. Do it instantly so he can't run up debts on a joint account that you're then half liable for. If there's a mortgage tell them too so hopefully he can't remortgage the house or anything until divorce is sorted out. Have child benefit put into your bank account.