Hi Erin,
I would not rely on an OT to diagnose or rule out Asperger's. Your son has some traits (the love of spinning things, the social quirks, the repetitive language) but not others (the compassionate behavior would be very unusual in an AS kid of this age). I'd go to an autism center or a developmental pediatrician specializing in autism to get help sorting this out.
Our experience with OTs for our son with AS is not great. They tend to pin everything on sensory issues, which means they tend not to see other things that are going on. They are not qualified to diagnose neurological disorders. YMMV.
DeeDee
