Hello there! I am the mom of an 18 year old boy with autism who also has intellectual disability. Both are moderate to severe. Now at 18, he is still nonverbal. However, he can now say words and he can express his needs better. When he does use full sentences, it’s because he has been taught to say them and he is not able to have a back and forth conversation. That has not changed. But in our case, now that he’s older, we now have a better idea of how limited his language is. We try to teach him to function to understand the world around him better, because nonverbal children can learn. My son is now doing things we never thought he could do and we are content with that.
We also have a 13 year old typically developed girl. My children give me the best of both worlds.
I hope this comment proves helpful.
May you and your family have a blessed afternoon.

My 9 year old is also level 3 and still non verbal with speech therapy. Pictures, visual and physical cues have really helped a lot. He responds to us when when say things and has just started responding to the use of a tablet device, which was unsuccessful before.