Another lone parent here, when I left my ex I was working 20hrs a week to fit round school hours.
Initially I was entitled to some HB (on the basis that the family home was for sale and I had moved out due to marriage breakdown).
Once I had the equity from the sale of my house the HB stopped, of course, but I still had wages, CTC + WTC (about £400), child benefit and maintenance. I was lucky enough to be able to buy a house with mortgage with the equity, so my housing costs went down as rents are astronomical where I live.
It was tight but perfectly doable. Since then over the last 3 years I've increased my hours and worked my a* off for two promotions so I'm almost up to the limit for tax credits now. When DS goes to secondary school I will go ft and my wages will increase again.
I'm never going to be well off but we have a comfortable lifestyle - certainly we have less than some people, but a lot more than others.
I hope my DS is growing up understanding the value of work and that iPads, Xboxes and all the other status symbols of the 21st century don't grow on trees and have to be worked and saved for. I would far rather that than him grow up with the kind of awful entitlement and oneupmanship that a lot of people seem to exhibit these days.
The first thing you need to sort out, ideally before you leave, is a financial agreement. I highly recommend mediation if you can get your H to agree to it because the costs are fixed and you could get to an agreement in just a few sessions if you are PAYE and have fairly simple finances.