My third and youngest child is precisely twice that age (34 mths) and is still not doing some things on that list, possibly through lack of interest not lack of ability, she's not much for screwdrivers... she is (and was) of course doing many things not listed which may or may not overlap in skill level, but I am guessing was not as advanced at 17 months as your son. And equally I am pretty sure that she will be at least similar to her sister in IQ (DYS qualifying FSIQ). We also have the "wow! That's different" experience when spending time with other kids her age, which doesn't happen often.