I'd tell them curriculum time is abnormal for 3.5 year olds! He needs to be playing on the swings, riding a trike, running in the backyard and catching tadpoles. Curriculum time is for school age children, which he isn't.
Sounds like your son is not interested in reading time or curriculum time. I'm guessing he thinks it's more fun to run around and be active, so that's what he's doing. He sounds like a normal 3.5 year old to me. Just because he doesn't want to sit and listen to an adult talk about what he isn't interested in doesn't mean he has a problem! If I were you, I'd be looking for another daycare, it is not a good match for your family. Their expectations for your son are too high. You have pursued the idea of autism and at least for now a medical professional does not see the signs. Currently, it doesn't really matter if he has adhd, autistism or is just an active little boy (most likely!!!) What matters is that daycare is saying they are becoming frustrated with your son, and you do not want your son where he is not wanted. Believe me, he is old enough to sense that. Find another place for him, and keep this in mind as you search. Find a place that presents the material in a different way, has a different structure, and doesn't expect everyone to conform to a certain mold.