hi sresree
I thnk that as autism itself is not understood it would be just as difficult to see a astrological signature of autism.
one thing that stands out is that his mercury is conjunct the north node. this gives him intuitive powers and usually an ability to use words and ideas. it also is marker of psychic abilities.
my feeling is that he is speech delayed because he doesn't need words to get what he wants and he intuitively understands what is going on around him without verbal explanation. I suggest that even when you know what he wants, work with him so that he has to verbalize to get what he wants. this aspect is associated with intelligence but the psychic component of his mind is so strong he isn't using his verbal power.
autism usually shows a social withdrawal of some magnitude and/or not responding to social signals.
this behavior is shown in chart though I am not labeling him as autistic because as I have said, the causes of autism are not known.
he has venus conjunct to pluto on the nadir. this describes emotional introspective individual. as this conjunction is on the nadir ,these tendency are at the base of his personality structure. he will always be emotional introspective and withdrawn to a degree until he learns to trust he socialization process. so don't let him be characterizes as autistic for his lack of social skills. he is that way .ther are no "normal" people. normal is a definition of average tendencies. he is extremely introspective and trying to bring him out of these tendencies will not be helpful. he will take longer that the average child to become comfortable with the socializing process. reinforce his mind and give him stimulation to make him learn. he is smart and he will respond to development of his mind.
he also has Uranus on the descendant, so part of his personality is very excitable. with these opposite tendencies of deep reflection and extreme excitability, his behavior could resemble bipolar syndrome. but again this is how he is. he has two distinct dynamics , he is introspective yet excitable and interested in his environment. this can show changes of temperament that could confuse him .
this is more complicated as the Uranus/venus-pluto midpoint is conjuct to nessus. and the sun is square to nessus. with unquestionably is a very difficult pattern because it shows that he could be subject to emotional outburst alternately with extreme withdrawal. the point is that he has these tendencies and there is not some external condition or influence that are causing these tendencies which could be called autistic. if these tendencies were not it in his chart and he exhibited autistic behavior then it would be different. but these are the psychological tendencies in his chart.
Jupiter is conjunct lilth which again shows that he has excellent mental potentiality. this aspect gives a inherent understanding of how larger pattern interact as well as positive outlook emotionally. the difficult aspects could manifest as behavior that makes him seem antisocial or destructive but this aspect shows he is good hearted at his core.
his moon is conjunct to sedan which suggest you must always be coherent with him. do what you say . this an aspect of a truth seeker, he will respond to coherent truth action, words and thoughts, but if there are contradictions he will be less likely to respond. even as a child you must be honest with him even if you think he is too young to understand the truth.
finally, talk to him as an adult even now. don't try to baby talk him because he seems speech delayed. speak to him as a intelligent person which is what he is.
rahu