Astarion is the sort of individual where, if you truly want to put an end to his shenanigans, he either needs 24/7 forever supervision or a stake through the heart. There is no third path. He's not someone we can fix. In many a person's story, he was the villain. The evil characters all have this in common.
Additionally, his way of "apology" isn't words, but actions. Astarion is someone who has been made to lie a lot for Cazador. You know he's sorry when he actually changes his behaviour. That's not a comprehensible communication style to people who can't read between the lines, but certainly a trait that for once very highly is to blame on trauma.
