allonsy I posted this further up. Its a sensory checklist (most OTs will use a standard one but this one is online). It might be useful to order the things he has difficulty with.
Vestibular can show as: bouncing (seeking), never walks, skips and jumps (seeking)
Auditory can show as: rarely bothered by noise (under-responsive), loves loud music (under-responsive OR just to confuse you, could be that he used rhythm to 'organise' himself OR could be that he used loud to block everything else)
Visual can show as: sensitive to sunlight (over-responsive), dislikes flashes (over-responsive), likes brightness and TV (both are constant and predictable)
Proprioceptive can show as: seeking rough-housing (calming to a dis-organised sensory system), Loving crash-banging (ditto)
Tactile can show as: odd reactions to touch. (Maniacal laughter is usually sysmptom of overarousal/stress. I would follow it with deep pressure e.g. heavy hug, wrapping in a duvet, tug-of-war.) Over-reactions to unexpected touch, appears to be in pain.
The babyish voice etc I cant pin as being a sensory issue....but if the world is a very demanding place for you, adopting a babyish persona will attract more 'minding' from adults. And having a poor sense of vestibular/space/timing issues, would also make it difficult for him to understand when to stop talking, social rules etc.
Hope that helps.