Questions on autism signs or if we are overthinking

Hello! My wife and I are parents an almost 3 year old (turns three in January ) and we are not sure if there are signs of autism in him, if we are overthinking things, or if he is just being a child. I apologize for the long post in advance, but we have been doing a lot of reading which may be why we are just overthinking some things.

For background:

He has always met his milestones and is a great speaker. Or so we thought. We have been paying more attention now that we have been reading up on autism and he does like to repeat songs a lot and things us, or other kids will say. For example, we would be at a park and he would hear a kid shout something, he would then also shout the same thing back. Or of my wife and I say a funny phrase, he will say it back in a laughing tone a couple of times. We are not sure if this is Echolalia that we have been reading about, or, if its just a kid being silly. I will also ask him about his day at daycare, and he usually says " I don't know". If I ask him a yes or no question, he can respond, but he usually will not tell us what he did. Again, not sure if he can only script yes or no questions, or, just a kid who does not want to chat about his day.

He does typically look back at us if we call his name. It may take one or two times, but he will usually respond. I know kids take a while to process, so is it just that? Or is it typical for children with autism to take a while to respond when calling their names? I have read conflicting things on this. His eye contact is good but not great. I notice it more than my wife, and if I ask him to look me in the eyes, he typically wont. But I am also not sure if that is just because I usually ask him to look at me when talking about things he should not be doing.

He has somethings that I am not sure if they would classify as stims or not, and he only does them occasionally. Usually it is at dinner, he will hum while eating his food and will shake his head back and forth. It is usually just at dinner, and not at any other point. A main question I could not find was if autism "signs" are always present, or only every once and a while? Like is just this potential stimming at dinner considered a stim? Or does stimming happen much more often? He does play well with other kids sometimes.

He has two cousins he sometimes likes to play with, but he also likes his alone time. He seems to be more into parallel play than playing with other directly. When I pick him up from daycare he is often running around alone, but he does say he has friends that he plays with and if I ask if they are his friends, he says yes.

He does some pretend play, but mainly if we ask him to. He does not really like playing with toys too much but he always preferred to run around as his attention span has always been low. We did do the M-CHAT-R and he scored a 1 on it, but I am not sure how accurate our responses were.

My main questions are do these sound like typical kid behaviors? Or could they be autism signs? He does not always show signs, but he does every once and a while which is why I question it. As I mentioned above, we are really struggling with if we are just overthinking it all or not.