I think the first think you need to remember is that he is only 21 months old. He is still quite young, and children do develop at their own rates. It's true that he might never talk, and that he might never live a normal life. There's also quite a bit of chance that he'll develop speech, that he'll end up seeming more normal.

He'll probably never seem fully normal, but many of us here aren't, and truly, we can be fully happy people even if we aren't normal, even if we are disabled, and even if we aren't fully independent. If he never develops speech, he won't necessarily be miserable and unable to communicate. If he never develops speech he'll not necessary be incapable. If he always needs help he'll not necessarily be unhappy. If he does develop speech he'll not necessarily be unhappy either.

Your son is a person like the rest of us who has his sensory challenges. He's young. There's a lot ahead of him. I'm sorry that I don't know how to help young children.

I'm only an autistic (no speech delay) adult with severe SPD. But I know that even though I'm not entirely capable I can be happy. I did have speech therapy as a child, but that's the only professional help I got, and that was just in school.

I also know that my closest friend had a speech delay - she wasn't speaking at 21 months, and is going to college now. She's still very much someone who needs help, but she's successful enough that people don't realize she's autistic at first glance, unless they read her service dog's patch.

But there's a lot ahead of him. It's not hopeless.

(Has the possibility of autism been looked into - the description there makes me wonder.)

Hopefully someone with children sees this and responds.