To my knowledge, the theory itself isn’t available anymore publicly. But Kieran Rose (Autistic Advocate, YouTube) has the original five-minute summary video of it on YouTube that I watched late July last year. He explains the theory in condensed form.
My “Discussing Suicide as an Autistic Person Is a Trap” and upcoming “Autistic Chronophobia Revisited” articles are the most recent explorations of Dr. Milton’s theory. The second most important research I’ve found as you’ll see in “A Lifetime in Eight Years.”
I’d recommend watching Rose’s video.