Interesting Topic. Thank you for that. I'll read the whole thread once I have more free time.
For now, I can share my experience. My nephew is 3 years old and he is my whole world. He seemed to be obsessed with the order of items and some objects and loved staring washing machine for "hours". After a few talks with my sister, I decided to search for it and bought a book and read online articles.
I can't remember everything but it gave me the conclusion that he is not autistic. Autism is not directly about intelligence (some autistic people can a lot smarter than the common folk) and it has a very wide spectrum as you mentioned. It is sometimes not even recognizable until very old phases of life as in yours.
From what I remember, autistic people usually;
* Can't look at you in the eye when talking or listening. Especially talking.
* They can form a special connection and focus on certain items.
* They love doing the same thing over and over again. God how many times my nephew killed my back because we played the same game repeatedly for 8-9 hours. :))
As you can see, we ALL have and do those things so I do not see autistics any different than who are not. Just slightly different which is a good thing.
Why do I have a slight notion that possibly all the "you"s in here mean me? Do correct me if I'm wrong.
And you're welcome and thank you for sharing.
I'm not trying to discredit your own research or suggest anything, but given that autism or at least Asperger's is often described as a hidden condition, I'd still seek a professional opinion to be sure - just a suggestion.
Let's see if I can shed some more light on those bullet points.
"From what I remember, autistic people usually;
* Can't look at you in the eye when talking or listening. Especially talking."
It depends on the individual a lot.
I have Asperger's so I may not be a "prototypical example", but I sometimes think I may stare at people a bit too much, maybe even more, when I'm just observing them and not while having a conversation (e.g. someone sitting across the hall).
At the same time I tend to try to find a point to focus on - usually a spot on the wall, but never the person I'm talking to - when I'm intensely searching for/trying to remember some key piece of information that's eluding me in that moment.
"* They can form a special connection and focus on certain items."
My soft toys have their own pillow and those that can't fit on my bed occupy multiple shelves (and that's a whole zoo XD ).
Or how I panic if certain items aren't where they usually are (e.g. small, but important items such as my keys, student card and wallet must be in a specific pocket in my backpack at all times as soon as I'm done using them).
Also, interests tend to be very focused.
At some point, I probably read everything there was about wolves. ;)
Or someone might want to know everything about a specific breed of shark but has no interest whatsoever in usual fish.
"* They love doing the same thing over and over again. God how many times my nephew killed my back because we played the same game repeatedly for 8-9 hours. :))"
I'm capable of listening to the exact same song or a small set of them for hours on end. XD
Allow me to expand this point.
Routine is comforting.
As is being told of changes ahead of time so you can have time to adjust.
E.g. If someone moved furniture to clean it, I'd feel restless and unsettled if it wasn't put back to the original place.
I've also come across an article that described a small child almost having a panic attack just because he was taken to school via a different route that the usual road due to it being blocked or something along those lines.
It varies from person to person and from situation to situation, but generally a big enough change (especially unexpected) will cause a shift to adrenaline mode when you will be very uncomfortable and will desperately want more time to process the situation, but unfortunately the world won't notice and will still demand a reaction way too fast.
While overload it usually connected to sensory stimulation it can also happen if you don't have enough time to process and the demand for a reaction or an answer keeps "hammering down" on you.
I remember being in a small restaurant with my mother and one of her employees, the waitress walked over and started going over the selection of food in different menu options.
I was still having an inner debate about a sauce in the first set, while she was already on the third one.
It was too much information too fast.
I went "Hold up!" out loud.
It wasn't that she was loud or anything like that, it was just that I didn't have the proper time to process.
She left, I calmed down went over all the information in peace and then we could order.
Luckily she didn't hold it against me or anything (by now we're one of their regulars), but she did learn it's best to wait for my que before listing more food.
P.S. If I've stumbled into the territory of over-explaining, I didn't mean to.