Have read all your posts and you seem to have 2 issues, health anxiety about covid and then your DS SEN with possible undiagnosed ADHD. I think you need to take some medical advice on the second issue. Perhaps even post separately here without mixing it up with covid concerns.
SEN provision in the UK is atrocious. Suggest going private to get a diagnosis then you can agree the best way to approach his what you say are lack of social skills and force the school to put a plan in place for him.
Something to bear in mind that if school isn't causing undue distress then it's probably best to have him in so he can forge friendships so he doesn't feel more left out when he does go back in.
You might get better more positive advice if you ask other homeschoolers if that's the way you want to go long term. My lovely home Schooling friend tells me this lockdown school is nothing like normal homeschool she has always been out and about in museums and nature, wood school, music etc. Seems like it's hard to do the real home school experience at the moment.
You are also mixing up how things work in your home country with how things work here. It's going to be different if everyone else is in school and your dc starts much later. That's not the same thing as everyone starting at the same time at 7.
I get that it's a really difficult issue for you. Maybe best to try and take covid anxiety out of the mix and deal with what is best for him educationally absent that. Then balance up what his our your family risk is from Covid. If there is no one CEV in your bubble I think you should go with whatever you decide best addresses his social and educational issues.