I agree with @itsstillgood . You don't necessarily have to pay out for online school, nor do you necessarily have to "teach" your son in a school-style fashion. Home education can look very very different from school.
The fact that you didn't get on well with lockdown schooling doesn't suggest you'll make a bad job of home education. Home ed is far more flexible.
One important point to remember is that you don't need to have a detailed plan before you get started. Schoolteachers do, because it's tremendously difficult to keep the attention of several dozen diverse children who are all working on the same thing. But you can (and should!) adapt your approach as you figure out what suits your son. If your initial idea of making your child do 30 minutes of math worksheets first thing every morning is causing stress, try it in the afternoon. Or use a book he likes better. Or let him learn maths by calculating odds in poker. Or put maths on pause for a while and concentrate for the time being on subjects which build his confidence.
Experienced home ed parents often recommend starting off with a complete break from all adult-enforced learning, especially for a child who has had a traumatic time at school, who needs to recover and relax before he'll be ready to focus. During this time, let him do what makes him happy. You will notice things he's learning spontaneously. Maybe you'll have a discussion about politics, or see him writing about Minecraft, socialising online, learning empathy and negotiation skills by working through a dispute with a sibling, acquiring some life skills by using the washing machine or fixing his bike, or calculating how to get enough money for the new game he wants to buy. That's education too.
It will take a while to find your way. But with your son out of school, you have all the time in the world. Only in a group-learning environment is there a risk of being "left behind". When his learning is targeted to him and his needs, it doesn't matter whether he learns algebra at 12 or 14 or 17, whether he takes two weeks off for illness, or when he has a holiday.
Take him out now, and then figure it out as you go along. You can't leave him to be bullied any longer. The sooner you deregister him from school, the sooner he can feel safe in the knowledge that he won't experience bullying. That knowledge will make a huge difference to him.