OLC - cook the dinner if doing so, and eating it, would give you pleasure. Don't if it would stick in your craw. But don't base your decision just on him; do it for you.
In a healthy relationship you would cook dinner because you want to, and your H would appreciate your effort - and his appreciation would make you even happier.
Turning to the practical side - you don't know how you'd manage as a single parent. Do you mean financially specifically? I would start by arranging meetings with CAB and a divorce lawyer. They will be able to tell you what you're entitled to and how to go about getting them. (I might be wrong, but I don't get the impression that money would be too much of an issue for you?) I know you've posted elsewhere on MN asking for advice re benefits, but I think it would do you good to hear it face to face.
I suspect you'd manage a hell of a lot better than you do living this half-life.
You also say you're scared of being alone (or possibly lonely) with just DS. Why should you be alone just because you've separated from yout H? Sure you might not be in another relationship anytime soon, but you don't have to be lonely.
Out of interest have you ever lived alone? The trick is to be happy in your own company (or at least happier than you are with your H, which doesn't sound hard!).
Does your H ever go away on business/trips? Do you feel happier when he does - choosing the food you eat, the telly you watch, what time you go to bed, whether DS gets a special treat of staying up for a cuddle? That's how it could be in the future.
AgingGrace talks about the need to love yourself and she's absolutely right. Look at individual counselling; start doing things you enjoy purely for yourself, even if just long bubble baths; list all of your friends and think about how you could spend more time with them in the future; are their hobbies you could take up to meet people? how old is DS? He'll be company for you soon. Are any of the Mums you meet at the school gate nice? In my experience, if you ask someone if they fancy a cuppa 99% will say yes.