OCD behavior in Autistic child

Hello, My son is 10 years old and is Autistic. He is currently taking risperdol for voilent behavior which seem to be under control for the most part. except he thinks its funny to hit someone go figure. Anyway, he is showing alot of OCD type behavior. What I mean is that Every minute of every day he can only focus on one or two subjects and repeats what he sais all the time. Its like his brain cannot move away from the subject.  This can start meltdowns and problems with his daily living. Does anyone have any suggestions for a technique we could use to help divert the behavior or at least try? I have realized the level of patience my husband and I have developed but Im more concerned about his ability to be independent when all he can do is focus on these specific thoughts. Any help is appreciated.