sorry for your distress OP, didnt want you to go unanswered either.
Deciding to end it, telling the OH, and putting the wheels in motion are hugely scary and daunting. Dont let that put you off though.
Get legal advice asap, sort out benefits etc, get as much advice and practical help under your belt before you do anything. You need to know what you are walking into before you end things otherwise you'll have so much more heartache, esp with 4 dcs.
my ex point blank refused to move out as he said it was my decision and it should be me to go. So I did. Am now renting a house using housing benefit and am claiming all of the working/child tax credits. I work full time. I got all of this sorted out before I left. Made me feel more in control.
Was really, really hard, especially with the kids at first, but six months on and with the decree absolute in sight, Im happier. Regret obviously for the kids but the environment before was so destructive. Took 3 years to finally summon the courage to call time.
Arm yourself, prepare and keep strong. Best of luck with it all OP.