Opinions, anyone? Mine happens to be that accomodations should go both ways. The church should (and tried to) accomodate the family; likewise the family should have taken steps to accomodate the parisioners, who are clearly afraid for their lives (the kid has started someone's car on one occassion? Scary!), and the priest, who does not want legal action taken against himself or his church. I also agree with Ms. Cornelius that the child seems afraid of crowded church and communion (entirely possible - autism - being uncomfortable around large groups of people - tactile sensitivity) and additional therapy may be needed to address that.
The easiest solution that comes to mind would be for the family to take turns attending Sunday liturgy, with one of the parents staying home with the child, and then possibly taking him to a smaller service on a less regular basis. Weekly Sunday mass might be overkill for him at this point. That's what I would have done.