He was very verbally cruel to me yesterday, referring me to as a simpleton, repulsive. I am an RN and although I did take care of him somewhat, I didn't care for him according to his standards. He is equating this situation with how selfish I have been for the last 5 years, etc. A. Yes, in some cases, dependency issues that arise in relationships can exacerbate some personality and relationship problems. It may have been that he really needed your help but really resented having to need it.
People usually begin to act in ways to regain control or competency.
In this case, he lashed out, made disparaging remarks about you and threatened to end the relationship. For some people, control over the relationship is the most important factor in why they stay in. It may be helpful to explore for yourself why you do stay in this relationship. From this perspective, it appears that control may be a strong force.