I was in your shoes, nearly 2 1/2 years ago. I can remember it like it was yesterday.

Is your son verbal? Does he do sign language? I recommend Stanley Greenspan's books on Floortime. They helped us enormously. He teaches ways, verbal and non-verbal to maintain interaction and communication iwth your child.
Our daughter Zoe was dx'd at 21 mths. We were signing with her at the time, as she had no words. She liked the Signing Time and Baby Bumblebee videos. At the time she was receiving speech therapy through Early Intervention. Our kids are eligible for special ed preschool as young as 2 years old. If I were to give you one piece of advice, I'd look into preschool as soon as he hits 2.
I really thought Zoe was not prepared for preschool, and her speech therapist agreed. She had zero attention span, wouldn't answer to her own name, had huge sensory issues, etc, plus gross motor weakness, poor motor planning.
In hindsight, I should have sent her at 2 1/2. She's in her second year of preschool, and the changes have been amazing. All the kids in the class have special needs, but not all have autism. They also intermix with "normal" kids for much of the day, so they're exposed to good examples for speech, socialization, etc. She is now extremely verbal, is learning to share with classmates, wait her turn, as well as learning traditional skills like counting, colors, etc.
I noticed the families who send their kids in at 2 will sometimes only go 3 days a week, or only mornings, so there is flexibility, which I hadn't considered at the time.
You have a lot to think about, and I hope you'll feel good about coming here . If I can be of any help, please let me know.