@Anastasia2, you are currently in a false reconciliation. Your faithless P is still pursuing other women, in this case a teen.
He sounds obsessed and clearly can’t get enough of her — mentioning her excessively, messaging after hours, providing lifts, having lunches, and devoting days off to help her. And in my view, his participating in a discussion with this employee regarding her preferred names for penises is indeed inappropriate.
Both of you are triangulating your daughter, which is an unfair and damaging move. As @MadAntonia pointed out, P is looping her in to normalize his inappropriate agenda. He is banking on DD’s presence and their new friendship to help him gain more access to the 18 year old. You are also triangulating DD by asking her to speak to her dad, hoping he will listen to her. Yes, she came to you with concerns about his mentionitis, but it is your responsibility to tackle the problem by confronting your P, not hers.
I commented on your December thread. P was cheating on you while working away, and treating you and the children like garbage. In February you referenced your separation and shattered confidence. P had coerced you to always hold your head down in public to repel men, while he was acting single and cheating.
@Anastasia2, P learned nothing from your separation and is still up to his old tricks. Whatever recovery requirements he agreed to, he is throwing them back in your face and is once again riding roughshod over boundaries. His using DD to hide his grooming in plain sight is beyond despicable.
You need to bin this thirsty creep once and for all.