You write so well and are clearly very intelligent.
Hats off to you for your drive, and for all you have done so far. Your children should be immensely proud of you.
I have no practical advice about the educational ladder, but for a possible career, how do feel about staying in the area you show promise in - the photography? Art schools offer all sorts of avenues into interesting work, like graphic design, photography, theatre (costumes, props, etc).
I have a cousin who is a police crime photographer - not pleasant work for the most part and not at all artistic but it pays for her flat and car, and she does more arty work in her own time. She will have a police pension in the heel of the hunt. She had A levels in art, physics and English iirc.
Set your sights high.
Do English, maths and science GCSEs and take it from there. You might well be able to get all the way to obstetrics. You could also consider midwifery, and progress to a senior role in that profession. There are also allied healthcare roles like occupational therapy or physical therapy, or speech/language therapy.
Don't be afraid to pick up the phone and talk to admissions staff in colleges or universities about where you want to go and how to get there, even questions about financing it all. Colleges or universities might offer aptitude testing or direct you to reputable places that offer it.
I second the advice from a PP not to attempt coursework on your own. Do classes. You will benefit from the academic guidance of teachers and from the camaraderie of fellow students.