It's impossible to tell in this sort of situation whether someone has genuine intentions or not.

Some people with personality disorders do experience moments of clarity, followed be a desire and effort to get better, and then they do.

Some people with personality disorders will only pretend to have a desire to get better, in order to hook you back in and screw around with you some more.

So the real strategy you need for yourself, is to make sure you focus on your own boundaries, what you will and will not tolerate, and your own expectations, and your own feelings.

In the end it should not matter what someone was thinking or feeling when they abused you, all that matters is that they abused you. If you are willing to give him another chance, it is extremely important that you prepare yourself to have a zero tolerance policy on abusive behaviors, no matter what.

It may even be worth getting yourself your own therapist to help you with this.