OP After 23 years of marriage and a family, I can understand why you have needed more than 6 weeks from your awful initial shock, to want to throw the towel in.
However, the advice you are getting is what gives you you the best chance of recovering your marriage, if that is your objective. Regard this then as pain for gain.
SGB's advice about giving him a date is spot-on. But by that date, he also has to provide you with incontrovertible proof that this relationship is over and he has severed all connections with the OW. If he works with her, that means getting another job and in the meanwhile, keeping their relationship to professional contact only.
At the moment, your H thinks he has the luxury of time and two women fighting over him. There is no urgent incentive to choose. Make that choice urgent, for two reasons.
First, it will get you what you think you want, quicker.
Second, it will help your mental health.
I hope you haven't said that even if he ends his relationship, you can forgive. You cannot know that yet.