Not sure how to process feelings about my ex's death?

Those feelings just prove that you are human and not as heartless as some other people. The fact that you feel somewhat happy about it is because after the abuse that you have suffered by the hands of this man, you may feel a little justice. All of your feelings seem quite normal to me. I think that you should just allow yourself to feel whatever feelings that you are going through because that is your way of greiving. I also thing that that is the only way that you will be able to fully get over your experience with him.