My son has had his OT through the school, although I've recently decided that maybe the 1/2 hour a week they were able to provide wasn't enough; he still has severe problems and at this point we've accepted that he always will. So what do I recommend? I think you should ask the OT for exercises etc. to do at home to reinforce her work, so that the help your child does get is maximized. OT should probably happen daily, which means you are going to HAVE to be involved.
As for socialization, a few things I found helped a lot:
1) Lunch bunch weekly at school.
2) Me being a room parent at school (I got to know the kids, and they got to know me; it helps not only locate who would be good playdates, but it also gave me leverage when my son had conflicts with other children).
3) A carpool. My son spent 5 years in a weekly carpool with the child who is now his best friend. When we started, the two thought they didn't have much in common. Well, sitting in a car and chatting eventually changed that. They still don't have that much in common, but there is so much mutual respect and trust that it bridges that divide.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).