If you believe you are a victim call the authorities. I would also consult with an attorney to know your rights.
This reply should NOT be considered a legal opinion of your case / inquiry. At this time I do not have sufficient factual/legal documentation to give a complete answer to your question and there may be more to the issues you raised then I have set out in my brief reply
It may or may not be beyond the statute of limitations. But if you believe that he is a potential risk to other children you can report what happened to you to the police. They can conduct an investigation that can lead to charges being brought. You may also be able to speak to counselors or victim's advocates who can help you deal with your own issues. And yes, you can consult with an attorney who can discuss the particulars with you and help you get some relief.
The statute of limitations for criminal prosecution and civil suits of sex abuse of a minor is constantly changing and it may be too old to prosecute your step-father in criminal court and in civil court for damages. However, you can file a police report and inform child protective services of past sexual abuse which could make him ineligible to work around children. There are some exceptions for civil suits for damages and it is recommended that you consult with an attorney.
This information is not intended as legal advice and is intended only to provide the questioner with general information. This is not intended to answer any other questions with similar facts. This is a general answer and does not create an attorney-client relationship or an attorney-client privilege.