Do you by any chance have any alternative schools where you are? My kid attends a free school (that is, he's in the preschool group, but there's an elementary group, too) that I find very helpful for him. The teachers support academic drive in the children but there's zero top-down enforcement. (It's basically unschooling within a school, I guess.) For my kid, this effectively works out to a system where he goes a playgroup where the adults scaffold his social and emotional skills, and he then uses his parents to acquire whatever academic information he's currently interested in. I know there are older gifted kids at the school who do something similar, except they also use their teachers and some of the older kids to learn what they want to learn, so it's not all on the parents.
It can feel kind of alarming to step way out of the mainstream like this, but looking at my own kid, I just find it really hard to fathom that he could make a more normal school work for him. It feels to me, right now, that our choices will be either "weird alternative school+afterschooling" or homeschooling, but I'm open to other options. I do find it hard to believe that a conventional school with a top-down, large-group lecture model will work for him. But who knows, everything could change in the next five minutes!