Wait until your son is interested. Very very very few children are interested in programming at age seven. Something that most children enjoy at that age is sitting on a parent's lap while the parent shares what they are doing with the child with a focus on sharing rather than on the thing they are doing.
My observation based on limited anecdotal evidence is that an interest in video games does not correlate to an interest in programming among children (or adults). Video games seem like fun to a lot of people and programming only seems like fun to a very few people.
Good luck.
Have you tried cubetto, robot teaching kids programming even before they can write? https://www.primotoys.com/
There's great medical improvement in treating autism, especially in US - my simple understanding of those advancements is that they try to remove cause of autism which in many cases seems to be related to brain being damaged by toxins.
Wish your son lots of health! And fun quality time with you :-)
You can always hire a teacher that uses an interactive notebook language like Mathematica that is chock loaded with easy to use APIs for graphics sounds dictionaries graphs atlas data etc... I actually teach programming from the ground up using Mathematica -- send the email in my profile a message if you're interested in having your son try a few lessons. Inspiration is really key for young kids and I do provide that. I also have a few autistic/asperger spectrum students so thats a plus. Gotta know how to communicate best - I'm sure you know as a father that unless you gain their interest, certain pursuits are a hard sell. Thats why languages that have a lot of ways to do things and are in interactive notebooks, ie. Sage Jupyter Mathematica -- they make it much easier to give a child the vision and desire of things they can do if they learn more.
I can't help you, but you shouldn't be frustrated if you fail to find a satisfying answer. There aren't great or universal answers even on broader questions like, "How do I teach my child to code?" and even, "How do I teach a person to code?"
If he's really into PC games, does he play Minecraft? I've seen a lot of articles and books about teaching kids to program Minecraft add-ons. That will let him customize his own world a little more, and also give him a great reason to learn and stick with it.
Instead of coding, I am teaching my 15 year old autistic daughter Chinese, because she wanted this instead. It has been a fascinating year long journey thus far.
His addiction sounds like he wants to do better and better each time. Perhaps learning a language and being able to read/write/speak more and more might fit with him.
His addiction is beating high scores and achievement unlocking for virtually every game he plays on ipad or PC.
I suggest you look into 2xe resources. This sounds like my oldest child, until we figured out how to get him adequate accommodation. A child who is both gifted and has challenges is often enormously frustrated. They tend to go for the only thing that works to get them some relief from the boredom of a bright mind trapped behind barriers and treated like they are dumb.
I also will recommend that instead of trying to find him a non-language outlet that you focus on helping him overcome his receptive and expressive disorders enough to adequately connect with the world around him. This was the approach I took.
I addressed individual pieces of the puzzle. I got him to learn to talk through things. I taught grammar, vocabulary, typing, and all the different pieces of how to write separately. We homeschooled for a long time and the first five years, he was incredibly resistant to writing anything. I did as much as possible without requiring him to actually write (other than working some on his handwriting). Then he discovered FanFiction.net and wrote several thousand words the first few days.
It is important for the child to be interested. That is the motive. But a 2xe child also needs help overcoming a lot of different barriers.
I have sympathy for what you want to do here and why, but I think you have a lot different things backwards.
My son has a tremendous interest in video games. He blogs about it and he has taken up modding games, but it has taken a long time to get here. I know a little html and css and I was able to explain coding to him in a way that made sense to him. He already knew a little html because of some forum he participated in. When they changed what was available, he kept using the font colors and other effects he liked because he had memorized the code. He didn't yet understand that was "coding."
I don't remember the discussion he and I had about all that, but I do remember it was a big deal to him.
There are lots of things that can help kids like this. You haven't really given the kind of information that would allow me to tell you specific things you could try. But, generally, you want to try to help him overcome his weaknesses enough such that they don't prevent him from doing what he wants, help him finds ways to get around things he just can't do (because they often aren't actually pertinent anyway) and support his interests.
I found it really helpful to do personality profiles and learn about learning styles. Instead of treating my son as a handicapped child who couldn't do "normal" things, I treated him as an interesting, quirky kid who needed a custom fit approach. I think this generally works better and gets better results. I also think it is a more accurate concept for people who are different.
If you haven't heard of Temple Grandin, I suggest you google her and start reading books and articles by/about her. She is autistic and also very accomplished. Another good resource is the book "Children with Emerald Eyes."
I have two siblings who are autistic. One is currently studying Artificial Intelligence and the other writes software for media environments (mainly TV). Both struggle with communication skills (empathy... they take EVERYTHING literally... they don't know when someone is disinterested...). One is 24 the other 31. Both are 'aware' of their Autism.
As both write software as part of their pursuits, I asked them what got them into software.
They referred to one single experience that started them on their paths. Funny as they have a large generation gap and went to different schools.
They told me about this robot they had in school. You would program steps (move forward 1 step... turn left 90 degrees.. move forward 10 steps.. etc.) and it would action them. They both became obsessed with it because in their eyes they were communicating with something and it was responding in a predictable and literal way. Both stated they found the predictability of software comforting.
I asked about software, and they said they would still recommend physical toys. Their reasoning was, even though they struggle with social skills, learning from apps would have further forced them to remain indoors.. reclusive.. Having a physical toy meant they were forced to interact with other people and learn from it.
You have Autistic son, so you'll understand his personality better than me. But if he shares the same traits as my siblings, then perhaps getting one of those toys will help.
Lastly, it warms my heart that you're taking his situation into account. It's controversial, but Autism can become a disability. But it can also become a trait which benefits someone in a way non-autistic people could ever attain. Apologies if this is patronising, but having an autistic child can be difficult, but it sounds like you're on a better than worse path. :)