Pax, glad you are feeling more comfortable in sharing more.
What is to be gained by outing the abortion expense? I have no idea how much they cost, but I'm guessing not significant. If your gut is saying don't do it, then I would go with that. How you feel about yourself is far more important than what he thinks about you or feeling the need to get back at him in some way. If you do list it, why not put "third party medical expense" so that it shows you are focused on the money (which is your right) and not the salacious aspect of it. He knows that you know.