I really feel for you, and you must be so worried. For some children school just doesn't suit. It has also been a time of great change for you both, so that won't have helped. Can you speak with his father and explain how very anxious your son is? He is his father and should be helping to support his son. It is most unfair on yourself and your son to just abandon you and his responsibilities as a father.
I think you need some professional advice regarding some sort of maintenance, and wonder if you have joined any home ed groups. Someone I think will come along and advise you on this. There can be a wealth of support out there to help you.
Do you have any family or friends to help you, for instance if you looked for part time work?
I thnk, in the first instance keeping your son happy and well should be your priority, seeking advice regarding maintenance from your ex, and making contact with other home edders locally for support.
I know work and home ed can be done, but it takes some good advice and a bit of thought.
Sorry that I can't help more, but am sending my best wishes to you and your son. You are obviously a very caring mum and are doing your absolute best for him.
I hope you sort something out, sure you will find a way through this. 