A person's age or an age gap in a relationship is not an indicator of abuse or likelihood to abuse. Look at the number of teenagers in emotionally or physically abusive relationships. Look at the number (majority, thank goodness) of 40 year olds that don't abuse their partners. The only way I could see an age gap as a possible indicator that something is wrong is when the person pretty much exclusively forms relationships with people significantly younger and attempts to control and steer the relationship.

If you think you're being abused, get the heck out or at least, get some distance. I would think that would be a sign that either you are and your feelings are being undercut or you are in a place that means you don't trust the person and have trust issues.