@Tinkerbelle1971 now is a very good time to try home ed and see how you get on. Here's why I say that.
Though GCSEs are not required, most home ed teens do choose to sit a handful of them, as that is usually the best way to get access to the next level of education. Doing GCSEs or IGCSEs outside school gives great flexibility - your child can do whichever subjects suit them, any number of subjects, and at any age. For example, home ed kids often spread them out by sitting a few at a time in order to concentrate and reduce the stress of juggling many subjects all at once. If your child is bright and keen, they can start at an earlier age. If your child isn't quite ready, they can delay.
However, arranging exams is quite tricky. There is a lot for the parent to learn about the different syllabi, exam centres, and options for how to learn the material. Many HE parents report that the years during which their kids are preparing for exams are harder work and less pleasant than the years before and after. Better than if the child were at school, perhaps, but still hard.
For this reason, starting home ed with a 15yo or 16yo is a steep learning curve - in at the deep end without time to relax and settle in. It's also more of a commitment than starting home ed at any other age, because if home ed didn't work out, the child can't slot back into school very easily, having missed a critical bit of the inflexible school-based GCSE exam preparation.
By contrast, if you start now, you and your son can take your time, let him have time to recover from his difficult school experiences, discover how and what he wants to learn, and adapt to this new way of learning. If home ed doesn't suit your family, your son could return to school in good time to start on his GCSEs. If it does suit, he can experiment with different approaches to learning. You and he can figure out what he needs. You can gradually get yourself up to speed on what will eventually become your Mastermind specialist subject: arranging home ed exams.
So I would say if you think home education might be a good option for your son, take the plunge sooner rather than later. Try it and see whether it works. Every week you delay is another week he is in a stressful environment. You can figure out the details as you go along; you do not have to have a detailed plan and stick to it. The worst case scenario is that home ed doesn't work out for him and he goes back to school, but at least you tried and ruled out an alternative. What do you have to lose?