The example of Sandy and Ray is the proof you can have a normal relationship with an Ex. Even a terrible abusive manipulating Ex.
This is because having analysed the relationship, learning the twisted mind of the Ex you don’t fall for his lies, tricks, deceptions, or his attempts to manipulate you.
You learn not to reveal you see through him. You learn not to react. You learn not to bring up the past.
You adopt silence.
What abusers thrive on is goading a person to react. One the victim reacts the Abuser can respond. When the potential victim does not react, the Abuser can not respond.
Further, to mention the past in any accusatory way; “You punched me in my face and broke my tooth!” pleases the Abuser. You remember. It still bothers you.