Physical & Emotional Abuse Support Group
Abuse is a general term for the treatment of someone that causes some kind of harm (to the abused person, to the abusers themselves, or to someone else) that is unlawful or wrongful. No one deserves abuse, period. Abuse can be emotional, physical, or sexual.
Everything you are saying makes sense & is normal given the situation you've come out of. It takes time, & doing some personal work, to get to the point where you can let go.
You are not failing because you love this person, You are not failing because you sometimes want him back. It wouldn't be healthy for you to go back, & you know that based on what you've posted, but don't beat yourself up for needing time to come to terms with that.
As often as possible, when you find yourself thinking about him, pull your focus back to yourself & your own life. See your friends, get out & meet new people, take care of your body & your home. Spend time with your family if you are able.
Also, the loving side is very recognizable. My abuser seemed to be drawn out of a romantic movie when he was in a good mood, and the complete opposite when he isn't. It makes you messed up and draws you to cherish an idle hope that he will ever become that permanently sweet person. In my case he was this guy after a while in the relationship for like 3 days on 7.
Wishing you a lot of success