Begin homeschool
Your son says he wants to homeschool. What does he picture as what he would be doing? I would listen to what he thinks he wants, and work with him; let him know what you think he should be doing, and work together on it.
I have several children with ADHD. For elementary ages, we did things together as much as possible: science, history, art, at the level of the oldest child, with the younger ones tagging along and getting whatever they could out of it. Math we did at the same time but each working at their own level. I read aloud to everyone and we discussed as a family. Individual reading skills we did individually.
I found it much easier to require household work be done, rather than requiring much written work. That way my children learned that things must be done when they must be done, with obvious consequences: if dishes are not washed, we have no clean dishes to eat with; if clothes are not put into the wash or not put away after being cleaned, we can't find them to wear them. Math doesn't have an obvious result if it's not done.
We read aloud and discussed, played games, did things outside every day, ran around the house, dug in the garden, played in the rain; two of my children had a need to get up and pace or bounce around after less than an hour of sitting still, so I let them. I had to remind myself to not hound them and remind myself to call them back to finish--or to get far enough that we could count it as "having done some". Elementary ages don't require a lot of time in the day; we did about 2 hours of stuff, including gym/running around as part of that time, and called it good. Then there were bedtime stories for fun and bonding as a family.
If they're not getting along with each other, hitting or fighting or arguing or getting into each other's stuff, I found it helped to just drop schoolwork and deal with the behavior. It's more important to me that they grow good relationships and learn how to get along with people while they're young. This will pay off in the future; they have years yet to get to more intense schoolwork.
I did not try to stick to a grade-specific curriculum; each of my seven children has been different and I'm not measuring them against a standard. However, I did assemble portfolios of their work at the end of each year when they were little. It helped to see their progress. I had no plans to put them back into any formal school, so I did not need to meet someone else's idea of where they should be academically. Having said that, schools know that no two children are doing exactly the same; schools can and should work around that, so don't bend yourself into pretzel knots trying to get your child to learn XYZ things for next school year.
Your relationships with your children are more important than any textbook or worksheet.