This is a horrible situation for you and a really difficult one to manage. A man of that age dating a teenager is digusting. It says everything about the sort of person he is. Sounds like she’s been well and truly groomed by him.
Is he her superior at work?
It says everything that it’s her worried about losing her job and not him.
There will be zero common ground between them just a huge imbalance in power and life experience.
If they stay together he won’t want her going off to uni as no man in a relationship with a teenager is going to have a healthy ego and is likely to be controlling.
@connie26I get that you don’t want to push her away but you also cannot validate and give your approval for this. She needs to see you trying to protect her and hold firm whilst making it clear you love her, always will and you want her to trust you and be able to come to you.
She may not want this now but in the future she may look back and appreciate this.
Keep talking about healthy relationships, power, respect and positivity.
As for not telling her dad, I think this is wrong and again helps keep this hidden which will do her no favours.
If you tell him, explain to your daughter first that he needs to know and It’s not fair on you to have to hold this worry alone.
Then you take responsibility for talking to him. Make it absolutely clear he can’t go off on one at her or the creepy sex pest because it will make things worse.
He can’t be acting the big man and trying to white knight the situation as the last thing she needs is him exploding and causing a drama.