you can like the person but not be able to deal with the disorder. If he is not getting help for himself such as DBT or making any attempts to manage his behavior, then it makes sense that you'd move on.
It would be better for you to find strength and halt the contact at least until you see him making some behavioral changes within himself. Otherwise, you'd find yourself on the same roller coaster as when you were together. You do not want to give him any false idea( because it is going to be interpreted an opportunity by him), and you do not want to be the codependent partner/friend for him.
Say Goodbye to Your PDI (Personality Disordered Individuals): Recognize People Who Make You Miserable and Eliminate Them from Your Life for Good! by Stan Kapuchinski (Paperback)