OP. I was a single parent of 5dcs.
My ds was newborn, my other ds was two and a half, my elder dcs were 10, 11 and 13. I had horrific postnatal depression, and could barely leave the small flat we lived in.
I developed crippling OCD that made life even harder.
The emotional abuse and manipulation from the scumbag I had children with, carried on for two more years - until I said no more! 
I cut contact completely and made a life for us, with family and good friends to support us.
Now, eight years later, all three elder dcs are at university, after completing their A levels. Two live out, and all have loving successful relationships. My youngest dcs are thriving at school, and I work myself (something I never thought I'd be able to do).
I supported my dcs singlehandedly, went to parents evenings alone (or with a baby or two!) , decorated, fed and clothed them all.
We no longer see the 'father' and I give thanks for that daily 
You can do it OP. It's good to be prepared. I am organised and love a routine, but just focus on getting through the day at first.
I was told this by a good friend in the early days, to find something everyday that makes you smile. Whether it's dancing madly with your dcs, praising their schoolwork, or laughing at a funny joke.
Anything at all. Find some joy in your day.
After a while, you will all adjust, and hopefully things will become easier, and the joy will be easier to find.