Your DC all sound wonderful, it is lovely to read about how they have grown and developed. I take comfort in these replies because it's something of an insight, perhaps not how DS will turn out himself but to hear about the potential in other children and young adults with ASD. Thank you 
If I'm to look at the positives in DS' case, there are plenty. I'll share them with you.
He can tell me what he wants now (usually juice - which he is obsessed with) but many other things such as dinner, cookies, penguins (one of his favourite cartoons Happy Feet), bath, dummy, blanket etc.
He can ask for his grandma, me and his dad when he wants either of us. He shouted for me to come to him for the first time ever last week and I could have cried! His pronunciation is a bit off and he calls me "money" 
Every morning he comes and climbs onto my bed and announces "want chris" which means he "wants crisps"
He can count independently from 1-30, he knows many colours, he knows and can recite his ABC. He can sing along with some songs. There is just no back and forth comms yet, other than the fact he can answer "Yeah" if I ask him whether he wants something.
He has a good understanding of how to use his tablet which surprises me for a child of his age given his SN, he has been navigating it like a pro since being under 2.
He is more tolerant of other children than he was a year ago and will now happily play with others (chasing, playing boo) rather than just parallel play.
He now thoroughly enjoys baths whereas before he couldn't tolerate them, too much going on sensory wise.
He used to be terrified of the Hoover and go into meltdown but now he can tolerate that too.
He wears ear defenders if we are going somewhere busy and he accepts those now whereas before he wouldn't let me put them on his head.
Hair cuts used to be impossible and he'd thrash and scream but now sits there happily.
When I focus on all of the above the future doesn't look as bleak as it does when I focus on the negatives (aggressive meltdowns, head banging etc)
He began to point a little this year too which was a milestone he never met when younger.
He's quite delayed in some areas but in others I dare say he's maybe a little bit advanced? Like knowing his ABC and being able to count to 30 before the age of three.