You have pretty much done everything that you can do. You can call AppleCare and ask to be transferred to the Account Security team to set up new security questions for your Apple ID if your iCloud account is the same.
Not sure what you are referring to with MacScan. In this case the people who got into your account probably did not hack through your computer they somehow learned what your password was.
@Clyde77: They have an iMac.