Don't try to tell an "authentic" story. Instead, tell an "inauthentic" truth.
Let somebody else write only allistic characters. You can write a character who is probably, or maybe, on the spectrum, but this does not need a huge reveal or internal struggle—it can just be a thing you do, among other things you do, as an author.
In first-person POV, it's challenging to convey who's speaking without a clunky or clichéd paragraph of self-description.
Adding or subtracting a character in the middle of creating a lengthy work is nearly as challenging as breaking up with a longtime life-entangled partner.
Draw on the best of the way the world is and has been, as well as your most optimistic hopes for what it could be. The real world is very unfair to those on the margins. Use your writing to make up for it.
You're operating by improv theater rules, where as soon as a character introduces a new idea, you say "yes, and" to it. But this theater troupe answers to your direction.
The question underneath your question is: "Am I allowed as a commercial writer to do the thing I want to do as an artist?"
We're swimming in the narrative conceit that what makes extraordinary characters interesting is their extraordinariness and what makes protagonists interesting is that they're protagonists.
Lots of things happen that characters don't know about, or only hear about. That's part of life, and is perfectly fine to include in fiction. Instead of trying to fix it, have your characters react to it.
If you still want to write even after you let go of any feelings of being obligated to write, take some time to think about why. Are there ways to access those motivations and keep them in the front of your mind so you can gain some satisfaction and joy from them?