Great ideas from ommmward! It's true, you don't have to get permission or explain your decision to home educate, except to your child's other parent if relevant. You can just do it.
The issue of excessive use of screens is a common one, especially among parents of kids with HFA. It hasn't been a problem in my family, but I overhear it discussed often! There are various views on it. I think that by and large, home ed parents discover that it is not such a big problem as they thought it would be. For one thing, your child will actually learn a lot from what he is doing on the computer. For another, once out of school he has more time at his disposal, because home ed is so efficient (as ommmward said, you'll probably find that when your child is ready to engage with it, an hour a day of formal learning is plenty, and some parents like me do none at all). So, even if your son manages to find something to do on the computer which has NO educational value whatsoever - which is difficult to achieve! - he can spend many hours a day on the computer and still get a good education.
Having said all that, some parents nevertheless say that doing literally nothing except using the computer every waking hour for months on end seems like an unhealthy habit, which interferes with their child's opportunities to get exercise and engage with daily life through shopping, talking to parents, helping out around the house, etc. A variety of methods are tried, with most people finding that what is appropriate one year needs to be adapted the next year.
If you can get along to a local HE group I am sure you will find other parents to discuss this. If that isn't practical, why not start a thread here for ideas? That will help you think through what might work for your own son, which isn't going to be the same as what works for the next kid.