OP your son sounds fine to me. I agree with pp that there is no particular reason to push learning to read or whatever this early. Sooner or later your kid will read, do arithemtic, and whatever; it really doesn't matter if it's at age 3 or at age 6. Best if he learns it because he has reached the point in his own development where he is truly interested, rather than being 'taught' to do it because that's what the adults around him deem appropriate.
By the way my DD1 has been in Montessori day care/preschool since 18 months because DH and I both work ft. I think she benefits a lot from being there but not for any instructional/academic reasons, rather the social experience of being with a regular group and learning to make friends and negotiate with others. That I think is really useful, but learning numbers/colors/abcs? Nah.