You sound to me as if you are fundamentally mismatched in attitudes to money - and thus life.
You want savings, you want to spend frugally, you look for the best deals, you don't spend frivolously, you are willing to compromise.
He is a spendthrift, who spends all he has, on nice-to-haves like Sky Sports, alcohol and magazine subscriptions while paying only £50 A MONTH TOWARDS FOOD FOR HIS WIFE AND CHILD.
You have big problems.
I would seriously consider leaving. You can work more and get help with tax credits etc. He will need to pay maintenance. You're not scared of living frugally. You'd probably end up better off than if you stayed with him.
Your future is him resenting you for controlling his spending, and you appeasing him by doing all the hard work to budget and scrimp and save and go without yourself so that he doesn't sulk like a baby.
As your DC grows up, and gets more expensive - shoes, football kit, activities, entertainment (teenagers are very expensive) - then you will find it hard not to affect his quality of life.
Think very very carefully.